US President Joe Biden was to hold crisis talks with his national security team Monday as fears grow of an Iranian attack on Israel in retaliation for the killing of a Hamas leader in Tehran.

Biden will also call Jordan’s King Abdullah II as part of a flurry of diplomacy aimed at preventing the situation in the Middle East from spiraling into an all-out war.

The United States has deployed extra fighter jets and warplanes to the region to support Israel, as reports suggested Iran could respond as soon as Monday to the killing of Hamas political chief Ismail Haniyeh.

Biden was due to meet his national security team in the Situation Room in the White House “to discuss developments in the Middle East” after flying back from a weekend at his home in Wilmington, Delaware, the White House said.

Vice President Kamala Harris, who is expected to announce her running mate for the 2024 election within the next couple of days, will be among those in attendance.

The meeting is set for 2:15 p.m. Washington time (1815 GMT) – after nightfall in the region, where it will be 9:15 p.m. in Tel Aviv and 9:45 p.m. in Tehran.

Biden was calling King Abdullah before leaving Wilmington, the White House said.

Iran has blamed the Haniyeh assassination on Israel, which has not directly commented on the attack, and sworn revenge. The killing came hours after an Israeli strike on Beirut left Hezbollah military chief Fuad Shukr dead.

‘Maximum restraint’

US Secretary of State Antony Blinken told his counterparts from the G7 nations in a conference call on Sunday that any attack, which he expected to be a joint undertaking between Hezbollah and Iran, could happen within 24 to 48 hours, as early as Monday, US news site Axios reported.

Blinken asked his counterparts to place diplomatic pressure on Tehran, Hezbollah and Israel to “maintain maximum restraint,” it added.

Blinken also emphasized the need to calm regional tensions in a call with Prime Minister Mohamed Shia al-Sudani of Iraq, where some Iran-aligned groups targeted US troops earlier in the Gaza war, the State Department said.

White House Deputy National Security Advisor Jon Finer said on Sunday that the United States was “doing everything possible to make sure that this situation does not boil over.”

The tensions also appeared to have torpedoed US hopes of any immediate ceasefire between Israel and Hamas in Gaza

Biden and Israeli Prime Minister Benjamin Netanyahu appear increasingly at odds on the issue, despite a meeting at the White House less than two weeks ago.

Biden said on Thursday that he had a “very direct” phone conversation with Netanyahu pushing him to reach a ceasefire deal.

He told reporters that the assassination of Haniyeh had “not helped” with the situation.

The conversation became heated, with Netanyahu pushing back against suggestions that he was deliberately trying to sabotage efforts to reach a ceasefire and hostage release deal, the New York Times and Axios said.