The US is seeking to deter Iran from carrying out a retaliatory strike against Israel with concerted declarations of commitment to Israeli security, while at the same time trying to prevent the outbreak of a major regional war, officials in Washington have said.

US officials still believe that a direct Iranian missile or drone strike is possible within the next few days, in retaliation for the Israeli bombing of an Iranian consular building in Damascus on 1 April, which killed a top Islamic Revolutionary Guards general and six other Guard officers.

The developments came as the US restricted the movements of its diplomats in Israel over security fears, the embassy said.

“Out of an abundance of caution, US government employees and their family members are restricted from personal travel” outside the Tel Aviv, Jerusalem and Beersheeva areas “until further notice”, an embassy notice on Thursday said.

Israel would rely heavily on US-supplied weaponry in any response to an Iranian strike, a point that Benjamin Netanyahu made implicitly on Thursday, by standing in front of American-made F-15 fighters at the Tel Nof airbase in southern Israel to tell reporters: “Whoever harms us, we will harm them.”

“We are prepared to meet all of the security needs of the State of Israel, both defensively and offensively,” the Israeli prime minister said.

The US hopes that strong messages of solidarity and support for Israel from Joe Biden and the secretary of state, Antony Blinken, could still deter Tehran from seeking to hit a target in Israel. A strike would mark a dangerously significant escalation in a long-simmering war, fought until now by proxy, or by strikes in third countries, such as Lebanon and Syria.

Blinken spoke by phone to Chinese, Turkish, Saudi and European counterparts “to make clear that escalation is not in anyone’s interest and that countries should urge Iran not to escalate,” state department spokesperson Matthew Miller told reporters on Thursday.

Biden said on Wednesday that Israel could rely on “iron-clad” US backing, and Blinken called the Israeli defence minister, Yoav Gallant, to tell him that Washington would “stand with Israel against any threats by Iran and its proxies”.

Nevertheless, if Iran does strike Israel directly, the US is likely to urge caution in Israel’s response, in an effort to forestall an uncontrollable escalation into a conflict that could draw in the considerable US forces in the region.

US officials say much will depend on the specifics of any Iranian attack. If Israel intercepts incoming missiles or drones, or if they fall harmlessly wide of their mark, the Biden administration will appeal to Netanyahu’s government not to act rashly. If any Iranian attack causes significant Israeli casualties either on Israeli soil or at any Israeli mission or institution abroad, however, Israel would be entitled to a forceful response in the eyes of the administration.

The head of US Central Command, Gen Michael E Kurilla, arrived in Israel on Thursday, Pentagon spokesperson Major General Pat Ryder told journalists, reportedly to coordinate the response to the anticipated Iranian action with his Israeli counterparts.

The possibility of an Israeli conflict with Iran or with its Lebanese ally, Hezbollah, is one of the reasons the Biden administration has given for resisting calls from many in the president’s own party to restrict arms supplies to Israel over the conduct of its war in Gaza.

Meanwhile, the prospect of an Iranian strike could also be hampering a long-awaited hostage-ceasefire deal in Gaza, officials in Washington said. They point out that the Hamas leader inside Gaza, Yahya Sinwar, had sought to ignite a regional war with the massacre of Israeli civilians on 7 October, so he would be unlikely to embrace a truce agreement at a time when such a conflagration looks more possible than ever.

The Iranian foreign minister, Hossein Amir-Abdollahian, has spent the past two days consulting counterparts in Saudi Arabia, Qatar, the United Arab Emirates, Iraq and Turkey.

The Iranian minister also travelled to Damascus to see his Syrian counterparts, and to Oman, the country most likely to act as the intermediary in sending messages to the US. In Muscat, Amir-Abdollahian said the US could not “shirk its responsibility in fully and absolutely supporting Israel’s combined war crimes”.

While in Oman, Amir-Abdollahian also passed on a message to Washington that Iran would not act hastily, but would respond to Israel’s attack in a way that aims to avoid major escalation, Reuters reported.

Russia and Germany both urged restraint. The German airline Lufthansa, one of only two western carriers still flying to Tehran, suspended its flights there, while Moscow warned Russians against travel to the Middle East.

The German foreign minister, Annalena Baerbock, also spoke with the Iranian foreign minister and urged Tehran to show restraint.

The Iranian readouts of the phone calls did not focus on the possible Iranian response to the Israeli attack but on the need for Gulf states to do more to put pressure on Israel to agree to a ceasefire in Gaza.

Amir-Abdollahian is still planning to travel to the UN headquarters in New York next week, raising doubts an Iranian missile attack on Israeli soil is imminent. An attack on the Israeli-occupied Golan Heights has also been discussed.

On Thursday the Kremlin called for all countries in the Middle East to show restraint to prevent the region from slipping into chaos.

The Kremlin spokesperson, Dmitry Peskov, said there had been no requests for Russia to mediate between Israel and Iran, although he said the Israeli strike on the Iranian consulate was a violation of all the principles of international law. Moscow has advised its citizens not to travel to a range of states, including Israel, Lebanon and the occupied Palestinian territories.

Iran’s supreme leader, Ayatollah Ali Khamenei, warned again on Wednesday that Israel “must be punished and will be punished” days after one of his advisers had said Israeli embassies were “no longer safe”.

The Israeli foreign minister, Israel Katz, swiftly replied to Khamenei on X, warning that “if Iran attacks from its territory, Israel will respond and attack Iran”.

There is an open debate inside Iran between diplomats and academics about the best response to what they see as psychological warfare. At one point it was reported that Iran was using the consulate attack as a lever on the US to put pressure on Netanyahu to agree to a full ceasefire with Hamas.

There is some scepticism in Tehran that an attack on Israel is necessarily imminent, and suspicion that Biden is instead seeking to distract from the fact that his supposedly decisive and firm phone call with Netanyahu last Thursday had led to a doubling in the number of trucks of aid entering Gaza but not produced the flood of humanitarian aid into Gaza that US officials had been demanding.

A new crossing from Israel into northern Gaza promised by Israel has yet to be opened, though the Israeli military said that construction had begun, and a coordination centre aimed at preventing further Israeli bombing of aid convoys by having operational commanders in the same room as aid agency representatives, has not yet been completed.

The head of the USAID humanitarian agency, Samantha Power, told Congress on Wednesday that it was “credible” a famine could already have taken hold in some parts of Gaza, confirming earlier warnings from UN agencies