Iran’s Revolutionary Guard said a short-range projectile was behind the killing of Hamas political chief Ismail Haniyeh and accused the United States of supporting the attack which it blamed on Israel, state TV reported Saturday.

The televised statement, which reiterated a call for retaliation, said a rocket with a seven-kilogram (about 15-pound) warhead was used to target the residence of Hamas’ political leader in the capital Tehran on Wednesday, adding it caused heavy devastation. It didn’t share details of the residence’s location.

Haniyeh was in Iran to attend the inauguration of newly elected Iranian President Masoud Pezeshkian.

“The action was designed and carried out by the Zionist regime and supported by the U.S.,” said the Guard’s statement. It added that “the warmongering and terrorist Zionist regime will receive harsh punishment in the suitable time, place, and capacity.”

Israel has not confirmed or denied its role in the killing of Haniyeh, but Israel earlier pledged to kill him and other Hamas leaders over the group’s Oct. 7 attack on southern Israel that sparked the war in Gaza.

The assassination has sparked fears of a wider regional conflict and of a direct confrontation between Israel and Iran if Tehran retaliates.

President Joe Biden was asked Saturday night in Wilmington, Delaware whether he thought Iran would stand down. He responded: “I hope so. I don’t know.”

In April, Iran launched hundreds of missiles and drones at Israel, which said it intercepted 99%. The barrage came less than two weeks after a suspected Israeli strike in Syria killed two Iranian generals, and it marked the first time Iran had launched a direct military assault on Israel despite decades of enmity dating back to the country’s 1979 Islamic Revolution.

Iran does not recognize Israel and supports anti-Israeli militant groups including Hamas and Lebanon’s Hezbollah.