The US is deploying extra military assets near Israel to protect it from a strike by Iran that could come as soon as this weekend.

Officials said they had implemented “force posture changes” and deployed “additional assets” to the region in light of threats by Tehran to strike Israeli territory in retaliation for an air strike on its consulate in Damascus last week.

On Friday, the Pentagon was said to have been expecting an attack in the next 48 hours, which raised the prospect of a direct conflict between Iran and Israel for the first time.

President Joe Biden on Friday said he expected Iran to attack Israel “sooner, rather than later” and warned Tehran not to proceed.

Asked by reporters about his message to Iran, Mr Biden simply said: “Don’t.”

“We are devoted to the defence of Israel. We will support Israel. We will help defend Israel and Iran will not succeed,” he said.

The USS Dwight D Eisenhower, an aircraft carrier, has sailed north through the Red Sea, bringing it closer to Israel, while local media reported Washington was planning to station a missile-equipped vessel close to the Israeli coast.

The Eisenhower is deployed alongside a US Navy cruiser, the USS Philippine Sea, and two destroyers, the USS Gravely and the USS Mason.

An online flight tracker tool showed a cargo plane linked to the aircraft carrier taking off near Yanbu, a Saudi Arabian port city in the northern Red Sea.

The US Navy declined to comment on reports that it had increased its presence in the region amid reports Iran has warned the US not to defend Israel or get involved in the conflict.

John Kirby, the White House’s national security spokesman, told reporters: “I certainly can’t deny that we’ve taken a look at [US deployments] and made some adjustments, but I am not in a position to get into the actual details of what that looks like.”

Separately, the US has increased its presence on existing bases in the Middle East in anticipation of attacks by Iran or its proxy groups, including Hezbollah in Lebanon.

“We are moving additional assets to the region to bolster regional deterrence efforts and increase force protection for US forces,” a defence official said.

The State Department has advised its staff not to travel within Israel until the situation is resolved, while the UK, France, India and Russia have issued travel warnings to their nationals in the region.

There were no visible signs of panic in Israel on Friday as shoppers in Jerusalem went to get groceries and families enjoyed a sunny afternoon on cafe terraces before they closed for the Sabbath.

Israel’s foreign ministry did not comment on reports that some Israeli diplomatic missions had been partially evacuated and security stepped up.

An Iranian attack on Israel in some form has been threatened by the country’s Supreme Leader Ali Khamenei since the Damascus strike on April 1, which killed a senior Iranian Revolutionary Guards commander, Gen Mohammad Reza Zahedi and six other members of the group.

Israel has not claimed the air strike but is widely believed to have been responsible.

Mr Khamenei said on Wednesday: “When they attacked our consulate area, it was like they attacked our territory. The evil regime must be punished, and it will be punished.”

It is unclear whether Iran’s response would come in the form of missiles from Iranian soil or from its nearby proxies in Lebanon and Syria.

‘We’re taking this seriously’

Western intelligence officials are expecting attacks on military and government buildings in Israel, but do not think civilians will be targeted.

“I can’t speak to what the intelligence picture tells us in terms of the size, scale, scope of what that attack might look like, except to say that we’re taking this seriously,” Mr Kirby said, adding that the threat was “credible”.

“The revenge will come,” wrote Israel’s largest daily newspaper, Yedioth Ahronoth. “For the moment, the premise is that it will be very soon, in the next few days.”

Given its magnitude, a strike on military targets would be challenging for Israel to defend itself against, US officials told CBS News.

The officials said they hoped Iran would opt for a smaller-scale strike.

Other unnamed US officials told The Wall Street Journal that Israel was preparing for a direct attack from Iran on the north and south of the country as early as Friday or Saturday.

On Friday, Hezbollah, the Iran-aligned militia in Lebanon, launched around 40 missiles into Israel in retaliation for its latest bombardment of villages in Gaza.

The attack was partially intercepted by the Iron Dome defence system.

The Israel Defense Forces and Mossad have already approved contingency plans to hit targets in Iran in case it decides to launch air strikes on Israel, while the US is expected to offer military support.

Yoav Gallant, the Israeli defence minister, said that Israel and the US were “shoulder to shoulder” in facing the threat from Iran after talks with the US regional military commander Gen Michael Kurilla.

“Our enemies think that they can pull apart Israel and the United States, but the opposite is true - they are bringing us together and strengthening our ties,” he said.

The prospect of the US participating in the conflict, either to defend Israel or retaliate against Iran, came as Tehran reportedly warned the Biden administration to stay out of the conflict.

Iran warned the US via Middle Eastern intermediaries that any participation from US forces would be met with a military response, Axios reported.

In January, three American troops were killed by an Iran-backed militia in Jordan.

The UK has two warships in the region, with HMS Diamond, a Type 45 destroyer, operating in the Red Sea off the coast of Yemen. A Royal Navy source told The Telegraph it had no plans to join US operations off the coast of Israel.

A second Royal Navy warship, HMS Lancaster, is deployed in the Arabian Sea to counter drug and weapon smuggling.