Joe Biden has said he expects an Iranian attack on Israel “sooner rather than later” and issued a last-ditch message to Tehran: “Don’t.” “We are devoted to the defence of Israel. We will support Israel. We will help defend Israel and Iran will not succeed,” Biden told reporters on Friday. Earlier the White House national security spokesperson John Kirby warned that the threat of a significant Iranian attack on Israel remains “viable” despite Washington-led efforts, including calls to Tehran from the UK and Germany, to deter a serious escalation in the conflict in the Middle East. The White House comments came as several countries, including India, France, Poland and Russia, warned their citizens against travel to the region and Israel’s defence minister, Yoav Gallant, said his country was “prepared to defend [itself] on the ground and in the air, in close cooperation with our partners”. Later CBS, quoting two unnamed US officials, reported that a substantial missile and drone attack could be launched as early as Friday evening, as a number of countries urgently warned their nationals of the risk of escalating violence in the region, and Israel’s prime minister, Benjamin Netanyahu, convened a security assessment. Appearing to underline that report, Javad Karimi-Ghodousi, a member of the Iranian parliament’s national security and foreign policy commission, said: “After punishing the Zionist regime in the coming hours, this villain will understand that henceforth, wherever in the world it attempts to assassinate figures of the resistance front, it will again be punished with Iranian missiles.” Iran has threatened reprisals against Israel for a strike on the Iranian consulate in Syria on 1 April, in which seven members of the Revolutionary Guards including two generals were killed, sparking fears that an already volatile climate in the Middle East could quickly spiral further. Tehran’s foreign minister, Hossein Amir-Abdollahian, said on Thursday that Iran felt it had no choice but to respond to the deadly attack on its diplomatic mission after the UN security council failed to take action. Speaking to reporters, Kirby said the prospect of an Iranian attack on Israel was “still a viable threat” despite concerted efforts by Israel and the US in recent days to deter it. “We are in constant communication with our Israeli counterparts about making sure that they can defend themselves against those kinds of attacks,” Kirby said. He confirmed that the head of US Central Command, Gen Erik Kurilla, was in Israel talking with defence officials about how Israel could be best prepared. Israel has said it is strengthening air defences and has paused leave for combat units. On Friday, France ordered the evacuation of diplomats’ families and warned nationals in several other countries, including Israel and Lebanon, and alerts were issued by Canada and Australia. The US also restricted travel within Israel for US diplomats and their families. In its strong warning on Friday, the French foreign ministry advised citizens against travelling to Iran, Lebanon, Israel and the Palestinian territories and said French civil servants were banned from conducting any missions there. The advisories followed a number of media reports that Israel was preparing for the prospect of an attack from Iran, possibly as soon as this weekend. A US official told the Wall Street Journal that American intelligence reports indicated an Iranian retaliatory strike “possibly on Israeli soil” as opposed to against Israeli interests elsewhere, adding that the strike could come within 24 to 48 hours. The same report, however, also reported an individual briefed by the Iranian leadership as saying no final decision had been taken by Tehran. While analysts had initially speculated that Iran may not rush into a response, concern has grown in the last two days over the potential for direct conflict between Iran and Israel after years of proxy conflict between the two enemies. More recently experts have suggested that Iran now feels it is required to act militarily to restore its balance of deterrence with Israel. On Wednesday, Joe Biden said Iran was threatening a “significant attack” against Israel and that Washington would do all it could to protect Israel’s security. The US president’s comments in turn followed a televised speech by Iran’s leader saying the attack in Damascus was equivalent to an attack on Iran itself. “When they attacked our consulate area, it was like they attacked our territory,” Ayatollah Ali Khamenei said. “The evil regime must be punished, and it will be punished.” The Israeli military said it was fully prepared for any strike. Israel was “on alert and highly prepared for various scenarios, and we are constantly assessing the situation,” the Israel Defense Forces spokesperson, R Adm Daniel Hagari, said at a press conference. “We are ready for attack and defence using a variety of capabilities that the IDF has, and also ready with our strategic partners.” According to reports in the Israeli media, the IDF believes that Iran or one of its proxies are most likely to attempt to strike a military target rather than civilian centres, although some sites such as the Kirya, Israel’s defence headquarters in Tel Aviv, are located in city centres next to shopping malls, offices and restaurants. Concern over a significant escalation in the Middle East conflict, which has already drawn in Hezbollah in Lebanon, pro-Iranian groups in Iraq and Yemen’s Houthis, came as Israeli forces continued to fight Palestinian militants in the north and centre of the Gaza Strip. Residents of al-Nusseirat refugee camp in central Gaza said dozens were dead or wounded after Israeli bombardment from air, land and sea that had followed a surprise ground assault on Thursday, and that houses and two mosques had been destroyed.