Thousands packed Qatar’s largest mosque on Friday for the funeral of Ismail Haniyeh, Hamas’s political leader, hours after President Biden said his killing could hurt the monthslong effort to negotiate a cease-fire in Gaza.

Mr. Haniyeh, who was based in the Persian Gulf nation, had been a negotiator in the cease-fire talks between Israel and Hamas. His death in an explosion in Iran on Wednesday and the assassination of the Hezbollah commander Fuad Shukr in an Israeli airstrike in Lebanon on Tuesday have put the Middle East on edge, bracing for a possible escalation in retaliatory violence.

Asked by a reporter on Thursday night whether the killing of Mr. Haniyeh had ruined the prospect of a negotiated cease-fire in Gaza, Mr. Biden said, “It has not helped.”

He added that he had a “very direct” conversation with Prime Minister Benjamin Netanyahu of Israel earlier that day and had urged him to agree to a deal to stop the war in Gaza and free the remaining people kidnapped in the Hamas-led attack on Israel on Oct. 7.

“We have the basis for a cease-fire,” Mr. Biden said. “They should move on it now.”

Mr. Netanyahu’s office said on Friday that an Israeli delegation planned to travel to the Egyptian capital, Cairo, on Saturday or Sunday for negotiations on a Gaza cease-fire and hostage-release deal.

He also said that Israel was preparing for the possibility of a retaliatory attack.

“Israel is in very high readiness for any scenario — both defensively and offensively,” Mr. Netanyahu said on Thursday. “We will impose a very heavy price for any act of aggression against us from any front.”