The United States is preparing for an attack from Iran, according to senior Biden administration officials.

“The President and the Prime Minister [of Israel] spoke about these threats yesterday (as the White House noted in its readout),” a senior administration official said in a statement. “Our teams have been in regular and continuous contact since then. The United States fully supports the defense of Israel against threats from Iran. I will not go beyond that given the sensitivity of the topic and information based on intelligence sources.”

The concerns come after Israel bombed the Iranian Embassy in Damascus, Syria, killing a senior Islamic Revolutionary Guard Corps commander, along with several others. The airstrike killed the most senior Iranian military figure since the U.S. assassination of former IRGC leader Qassem Soleimani.

Iran has publicly vowed retaliation after the strike.

“[Israel has] gone beyond the red line,” Iranian Ambassador to Syria Hossein Akbari said Monday on an Iranian state media broadcast. “Iran has never left any crimes of the Zionist regime without an answer. So, definitely, the Zionists and their allies know that in proportion to the crime they have committed, they need to await a proper response on the basis of Iran’s choosing at the right place and time.”

Senior U.S. officials told CNN the attack is expected to be “significant” and that it is “inevitable.” One official said the attack is expected within a week.

The U.S. said it had no role in the strike and that it was only notified while it was being carried out.

Israel has been taking major precautions since its attack, canceling all leave for Israel Defense Forces soldiers. IDF officials asked Israeli citizens not to panic.

“There is no need to buy generators, store food and withdraw money from ATMs,” IDF spokesman Rear Adm. Daniel Hagari wrote on social media. “As we have done until today, we will immediately update any change if it is in an official and orderly manner.”

The U.S. and Israel are cooperating in bracing against attacks from Iran, with the prospect featuring prominently in President Joe Biden’s call Thursday with Israeli Prime Minister Benjamin Netanyahu.

Iranian proxies launched over 170 rocket and missile attacks against U.S. troops stationed in Iraq, Syria, and Jordan following the beginning of the war in Gaza. They halted attacks in February after three U.S. soldiers were killed at a base in Jordan.