The death of Hamas leader Ismail Haniyeh in an assassination attributed to Israel "has not helped" ongoing ceasefire talks with the group, President Joe Biden said on Thursday.

Speaking to reporters at Joint Base Andrews in Maryland after a call with Israeli Prime Minister Benjamin Netanyahu, Biden said, "We have the basis for a ceasefire. He should move on it, and they should move on it now."

Wednesday morning's killing of Haniyeh, Hamas's top "political" leader, "has not helped," he said, adding, "That's all I'm going to say right now."

The U.S. leader told journalists he was "very concerned" about the mounting tension in the Middle East. "I had a very direct meeting with the prime minister today. Very direct," Biden said.

A report in The Jerusalem Post on Thursday claimed that Haniyeh was viewed as an obstacle to closing a ceasefire agreement and that his removal might bring one closer.

In the hours following the assassination, Israeli Defense Minister Yoav Gallant informed US Secretary of Defense Lloyd Austin that Jerusalem remains committed to closing a hostage deal, "especially at this time."

Haniyeh died when a bomb exploded at his Islamic Revolutionary Guard Corps guesthouse in Tehran around 2 a.m. on Wednesday. Iran and Hamas have both accused Jerusalem of carrying out the attack.

Asked about the bombing at a press briefing on Thursday, Israel Defense Forces Spokesperson Rear Adm. Daniel Hagari said that "there was no additional aerial attack—not a missile and not an Israeli drone—in the Middle East that night and I won't say anything beyond that."

One hundred and fifteen hostages, both living and dead, remain captive in Gaza, more than 300 days after Hamas's Oct. 7 invasion. Dozens are believed to be alive, an official involved in the talks said last month.

Hamas has demanded that Israel accept an immediate ceasefire and withdraw all forces from Gaza, a demand that Jerusalem has rejected.

Netanyahu told lawmakers last month: "We are determined to return all our hostages. The key is pressure, pressure and more pressure."

Families of the captives held by Hamas this week expressed mixed feelings over Haniyeh's killing, with many saying they were unsure how his death would affect an expected breakthrough in the negotiations.