The U.S. State Department has approved the potential sale to Taiwan of about $75 million of advanced tactical data link system upgrade planning, the Pentagon said on Wednesday.

The sale comes amid heightened tensions between Taiwan and China, which claims the island as its own territory. China has never ruled out using force to take control of Taiwan.

The package would include Cross Domain Solutions, High Assurance devices, Global Positioning System receivers, communications equipment, technical services and other related elements of logistics and program support, the Pentagon said.

The Pentagon's Defense Security Cooperation Agency notified Congress of the possible sale on Wednesday.

Despite approval by the State Department, the notification does not indicate that a contract has been signed or that negotiations have concluded.

The Pentagon said the prime contractor will be determined in competitive processes.

US lawmaker who chairs China committee arrives in Taiwan

U.S. Representative Mike Gallagher, who chairs the House of Representatives select committee on China, arrived in Taiwan on Thursday with a delegation of other lawmakers and will meet Taiwan's president and president-elect.

Gallagher, who is being accompanied by four other lawmakers on a trip ending Saturday, has been a strong friend of Chinese-claimed Taiwan and a fierce critic of China.

"Time and again Taiwan has shown the world how to stand up to the CCP's bullying and not only survive, but thrive," Gallagher said in a statement, referring to China's Communist Party.

"The United States stands with Taiwan. By promoting deeper ties between our leaders and our economies we can enhance peace and stability across the Taiwan Strait."

China views democratically governed Taiwan as its territory. The government in Taipei rejects that position, saying only the island's people can decide their future.

Beijing routinely denounces visits by foreign lawmakers to Taiwan, believing it seeks to stoke tensions and interferes in China's affairs.

Taiwan says it can invite whomever it wants and that China has no right to speak for Taiwan's people.

Taiwan's presidential office said the group will meet on Thursday with both President Tsai Ing-wen and Vice President Lai Ching-te, who won election as Taiwan's next president at elections last month and will take office on May 20.

In December, Gallagher's committee issued an extensive list of bipartisan recommendations to reset U.S. economic ties with China, setting out legislative goals for 2024 that it said would prevent the U.S. from becoming the "economic vassal" of its chief geopolitical rival.

Gallagher said this month he will not run for re-election.

Gallagher, a member of both the House Armed Services and intelligence committees, has spent much of his time this year chairing the Select Committee on the Chinese Communist Party, a bipartisan panel charged with investigating U.S. relations with China and developing strategies to improve the country's ability to compete with China.

Taiwan calls on China to 'be rational' after deadly boat incident

Premier Chen Chien-jen said both sides had been aware of "restricted and off-limits sea areas" since 1992.

Taiwan called on Beijing to "be rational" on Tuesday following a deadly incident involving a Chinese boat and the Taiwanese coast guard, with the island's premier insisting it would protect its waters.

China claims self-ruled Taiwan as part of its territory, and relations between the two have soured in recent years.

Last week two Chinese crew members died after a boat capsized near Kinmen, an island administered by Taipei but located just five kilometres from the mainland city of Xiamen.

It was being pursued by Taiwan's coast guard for being within prohibited waters.

Taiwan's Premier Chen Chien-jen said Tuesday that both sides had been aware of "restricted and off-limits sea areas" since 1992.

"We will continue to protect these sea areas to ensure safety in our territorial waters and the rights of our fishermen," he told reporters outside Taiwan's parliament.

"We hope both sides can be rational, equitable and cooperate with each other to ensure the safety of the Kinmen-Xiamen waters so that the people from both sides of the strait can engage with each other in a healthy and orderly manner."

Taiwan's defence minister said the military would not get involved, leaving it to the coast guard to monitor waters around Kinmen, "because we want to avoid war".

"If we intervene, it will escalate the conflict which we do not want to see," Chiu Kuo-cheng told reporters.

"Let's handle the matter peacefully."

Beijing has never renounced the use of force to bring Taiwan under its control, and in recent years has ramped up the rhetoric of "unification".

It has stepped up military pressure on Taiwan by deploying warplanes and naval vessels around the island on a near-daily basis.

Last month Taiwan had a presidential election which ended in a win for the Democratic Progressive Party's Lai Ching-te -- a candidate Beijing considers a "separatist".

Taiwan's defence ministry on Tuesday said it detected 24 Chinese warplanes around the island in the 24 hours to 6 am -- a slight uptick compared with recent days.

- 'Strong indignation' -

Relatives of the two deceased crew arrived in Kinmen on Tuesday, accompanied by representatives of the Red Cross Society of China.

Li Zhaohui, a Red Cross representative, told reporters that the "vicious incident caused strong indignation in China".

"The purpose of our trip to Kinmen is to understand the truth, assist the family members in the aftermath, and bring back the two survivors," he said.

The families are expected to take part in religious rituals mourning the deceased, who will be cremated, and they will stay in Kinmen until Wednesday.

China had condemned the incident, with Zhu Fenglian, spokesperson of Beijing's Taiwan Affairs Office, saying Monday Taipei should facilitate the relatives' visit to "avoid further hurting the feelings of compatriots on both sides of" the strait.

Taiwan's coast guard had defended its actions during the pursuit that led to the deadly capsizing, saying the Chinese crew refused to cooperate with law enforcement.

It is not uncommon for Chinese and Taiwanese ships to accidentally enter the other's side.

After last week's fatal incident China announced stepped-up patrols around Taiwan's waters, and on Monday members of its coast guard briefly boarded a Taiwanese cruise ship to check the captain and passengers' details.

Kinmen legislator Chen Yu-jen said the tourist ship had sailed "about one kilometre" into mainland waters.

"When relations between the two sides were relatively peaceful, we would not board each other's boats... It's because at that time there was a tacit understanding and the two sides would not take tougher actions," she told reporters.

But now with tenser cross-strait relations, she urged Taiwan's tourist boats and fishermen to stay within their waters.

"This is the safest way," Chen told reporters.