Philippine President Ferdinand Marcos Jr. on Monday said talks on maritime cooperation between his country and Vietnam would be one of the cornerstones forged in a strategic partnership with its Southeast Asian neighbour.

"We hope to strengthen this aspect during my visit to promote peace and stability in our region," Marcos said in a statement before leaving for Hanoi for a two-day state visit.

Marcos is expected to meet Vietnam's top officials and work on agreements on coastguard cooperation and rice supply. Vietnam is a major rice exporter and the Philippines is one of the world's biggest importers of the grain.

Marcos said he hopes his visit would bring their relations to greater heights and "usher in a new era of friendship and cooperation", with talks on trade, investment, education and tourism, as well as "regional and multilateral issues of concern."

Vietnam and the Philippines have overlapping claims in the South China Sea, but have generally friendly relations compared to the heightened tensions between Manila and Beijing over disputed waters.

Ties between the Philippines and China have deteriorated this past year, coinciding with a tougher stand by Manila and overtures by Marcos to forge stronger military relations with the United States.

The South China Sea, a conduit for more than $3 trillion in annual ship-borne commerce, is claimed almost entirely by China via a U-shaped line policed by its vast coastguard fleet, which cuts into the exclusive economic zones of Vietnam, the Philippines, Malaysia, Brunei and Indonesia.

In 2016, the Permanent Court of Arbitration in the Hague said China's claims had no legal basis, a decision Beijing has rejected.

'I think it's the fentanyl': Philippines' Marcos hits back at predecessor Duterte

Philippine President Ferdinand Marcos Jr. struck back on Monday at his firebrand predecessor Rodrigo Duterte who called him a "drug addict", saying the former leader's fentanyl use could have affected his judgment.

"I think it's the fentanyl," Marcos told reporters shortly before leaving for Vietnam in response to claims made by Duterte on Sunday while speaking at a rally in his hometown Davao against moves to amend the country's constitution.

When asked about the drug use accusations and the call for him to step down, Marcos said, the former president "has been taking the drug for a very long time now...after five, six years, it has to affect him."

In 2016, Duterte admitted he used to take the highly addictive synthetic opioid fentanyl for pain relief after a motorcyle accident.

"I hope his doctors take better care of him," said Marcos.

Duterte also said Marcos was included in the drug agency's so called 'narco-list' that was submitted to him when he was still mayor of Davao city, a charge which the Philippine Drug Enforcement Agency vehemently denied.

Duterte's accusations came after his son, who is the incumbent mayor of Davao, called on Marcos to resign, citing his supposed failings to address criminality and a foreign policy that "endangers the lives of innocent Filipinos".

Former president Duterte has earned international rebuke for unleashing a brutal campaign against illegal drugs when he assumed power in 2016, killing more 6,000 dealers whom police said resisted arrest during anti-drug operations.

The International Criminal Court has allowed an investigation into the killings to resume, but Marcos said his government will not cooperate.

Ex-Philippine leader Duterte assails Marcos, accusing him of plotting to expand his grip on power

Former Philippine President Rodrigo Duterte is throwing allegations at his successor, Ferdinand Marcos Jr., and even raising the prospect of removing him from office, bringing into the open a long-rumored split between the two.

In an expletive-laden speech late Sunday, the former populist leader alleged that Marcos' legislative allies are plotting to amend the constitution to lift term limits and warned that could lead to him being ousted like his father, the late dictator Ferdinand Marcos. Duterte also accused Marcos of being a drug addict.

Marcos laughed off Duterte’s allegations in comments to reporters before flying to Vietnam for a visit. Marcos said he would not dignify the accusations with an answer, but claimed his predecessor is using fentanyl, a powerful opioid.

In 2016, Duterte said he had used fentanyl in the past to ease pain caused by injuries from a motorbike accident. His lawyer, Salvador Panelo, said Monday that Duterte stopped taking fentanyl before he became president in 2016.

“I think it’s the fentanyl,” Marcos said. "Fentanyl is the strongest pain killer that you can buy. ... After five, six years, it has to affect him, that's why I think this is what has happened.”

Members of the House of Representatives have been talking about amending the constitution, and Duterte claimed without offering any evidence that lawmakers who support Marcos, including House Speaker Martin Romualdez, are bribing local officials to amend the 1987 constitution to remove term limits so they can extend their grip on power.

Romualdez, who is the current president's cousin, has denied that claim, saying he wants the constitution amended only to remove restrictions on foreign investment.

Marcos has said he is open to altering economic provisions of the constitution but opposes changing a provision that restricts foreign ownership of land and other critical industries like the media. Philippine presidents can serve only a single six-year term.

Opponents of opening the constitution to changes include the Senate. It issued a statement last week warning its checks-and-balance role could be undermined if the House of Representatives proceeded with plans to pursue amendments in a joint session rather than by separate voting in the 24-member Senate and the 316-strong House.

The Commission on Elections said Monday it was indefinitely suspending all activities related to the effort to change the constitution, which requires the signed consent of about 8 million registered voters nationwide. The decision temporarily derailed moves to revise the charter.

The 1987 constitution, which is laden with safeguards to prevent dictatorships, came into force a year after Marcos' strongman father was ousted by an army-backed “people power” uprising amid allegations of plunder and human rights atrocities during his rule.

The speech put credence into months of rumors about a political split with his successor even though Duterte’s daughter Sara is Marcos’ vice president following their landslide election victory in 2022.

In recent weeks, Duterte’s supporters have been angered by reports of an unannounced visit by International Criminal Court investigators last month who are probing widespread killings during an anti-drug crackdown Duterte launched as president. The reported visit has not been confirmed.

Duterte, who became notorious for the harsh crackdown that left thousands of mostly poor suspects dead, claimed in his speech without offering any evidence that Marcos was once on a law enforcement list of suspected drug users.

“You, the military, you know this, we have a president who’s a drug addict,” Duterte said to cheers from a few thousand supporters in his southern home region of Davao city.

The Philippine Drug Enforcement Agency said Monday that Marcos was never on such a list, contrary to Duterte’s claim.

In 2021 when he was a presidential aspirant, Marcos' spokesperson showed two reports from a private hospital and the national police laboratory that said Marcos had tested negative for cocaine and methamphetamine.

The two men also have differences over foreign policy.

While Duterte nurtured cozy ties with Chinese President Xi Jinping and Russian leader Vladimir Putin while in office, Marcos has been seen as veering toward Washington over his country’s territorial disputes with China in the South China Sea. Early last year, Marcos allowed an expansion of the U.S. military presence in the Philippines under a 2014 defense pact.

Marcos succeeded Duterte in mid-2022 after campaigning on a promise to work for an economic turnaround after the coronavirus pandemic and bring unity in a country long saddled by crushing poverty and deeply entrenched political divisions.

Marcos led his own rally Sunday at a seaside park in Manila, which police said drew about 400,000 people after nightfall.

The rally was called to launch what Marcos says is a campaign for a “new Philippines” by reforming corrupt and inefficient governance and boosting public services. During the gathering, the president stayed nonconfrontational in the face of the escalating criticisms from Duterte’s camp.

“The 'new Philippines’ is not just a slogan,” Marcos told cheering supporters. “To those whose overheated imagination has been poisoned by toxic politics, the `new Philippines’ is no Trojan horse, it conceals no agenda.”

Addressing government officials and employees, Marcos called for an end to sluggish services to the public. “Distress calls must be responded to without delay. In whatever government office, red tape must be replaced with a red carpet,” he said to applause.

Rift intensifies between Philippines president and Duterte family

Philippine President Ferdinand Marcos Jr.

Former Philippine leader Rodrigo Duterte's son urged President Ferdinand Marcos Jr to resign on Sunday, calling him lazy and uncompassionate in a deepening rift between the two politically powerful families.

Marcos teamed up with Duterte's daughter Sara to make her vice-president in their 2022 election win. But cracks in the families' alliance have emerged as the incumbent has veered away from his predecessor's anti-drugs and foreign policies.

Sebastian Duterte, who is mayor of Philippines' third most populous city Davao, said there had been a resurgence in crime after his father's hardline campaign had been relaxed.

At a leadership forum, he also accused Marcos of endangering innocent Filipinos by allowing the Americans in, a reference to expanded U.S. access to military bases, including several close to Taiwan. The older Duterte had forged closer ties with China.

Sebastian Duterte also opposed Marcos' decision to restart peace negotiations with communist rebels, saying he did not know anything about the suffering of people living in areas that used to be rebel strongholds.

"You are lazy and you lack compassion. That's why we are unhappy," he said.

There was no immediate comment from Marcos' office.

MID-TERM ELECTIONS LOOM

He spoke just before Marcos took the stage at a government-led rally in the capital to drum up support for his "Bagong Pilipinas (New Philippines)" campaign, where he has promised to improve state services and budget transparency.

Marcos' alliance with the Dutertes was crucial to his presidential victory, so a souring of their relations could have implications in his bid to solidify his support base ahead of the mid-term Senate and congressional election next year.

Sara Duterte, who is also education secretary, attended the president's rally before flying to Davao to join her father and siblings at a prayer rally against moves to amend the Philippine constitution, which Marcos backs.

Some opponents of constitutional change, including the Dutertes, say it is driven by an agenda to change the political system and remove term limits, including that of the president, who can currently serve just one six-year term.

"He is putting politics first, their self-preservation ... rather than focusing on the job," Sebastian Duterte said.

"Mr. President, if you have no love and aspirations for the nation, resign."

Like her brother, Sara Duterte has openly defied some of Marcos' policies, including the peace talks with communist rebels which she said was an "agreement with the devil."

Asked for comment on her brother's remarks, Sara Duterte said on Monday: "I can only surmise he is coming from a place of brotherly love, coupled by the common sentiment that I do not deserve the despicable treatment that I am receiving from some sectors within the circle of the president."

Sara Duterte did not elaborate, but said she "will stay true" to her work at the education ministry.