The United States wants to kickstart talks on a proposal to achieve a ceasefire and the release of hostages in Gaza, U.S. State Department spokesperson Matthew Miller said on Thursday, after the death of Hamas leader Yahya Sinwar, which he called a "seismic event."

Miller told a regular press briefing that Sinwar had been the "chief obstacle" to reaching an end to the war, which began when Sinwar orchestrated an attack on southern Israel in which Palestinian militants killed about 1,200 people and took 250 hostages.

The Biden administration has worked unsuccessfully for months with mediators Qatar and Egypt to try to reach a deal that would see Israel cease operations in Gaza in exchange the release of hostages taken by Hamas in the attack just over a year ago.

In recent weeks, Sinwar had refused to negotiate at all, Miller said.

"That obstacle has obviously been removed. Can’t predict that that means whoever replaces (Sinwar) will agree to a ceasefire, but it does remove what has been in recent months the chief obstacle to getting one," he said.

Washington would now "redouble" its efforts and try to push forward the ceasefire proposal "that has been on the table for some time," Miller said, without detailing the proposal.

"I don’t want to predict too much what our efforts will look like over the course of the days because we are just hours after what is a seismic event that changes the nature of this conflict, but we believe it is an opportunity to try and bring an end to this war, and we’re determined to try and seize that opportunity," Miller said.

Secretary of State Antony Blinken has already spoken to the foreign ministers of Qatar and Saudi Arabia about bringing an end to the war and post-war arrangements for Gaza, Miller said.