US Secretary of State Antony Blinken on Wednesday expressed frustration that Hamas has submitted “numerous changes” to a US-backed proposal for a ceasefire and release of hostages in Gaza – a development that casts further doubt on the prospects of quickly securing the deal the US hopes will bring “an enduring end” to the war.

“Some of the changes are workable. Some are not,” Blinken said at a press conference in Doha, describing some of those changes as going “beyond positions (Hamas) had previously taken.”

Blinken, unlike an Israeli official who spoke to CNN earlier, did not go as far as to describe the response by Hamas as a rejection of the proposal, and said he believed that the “gaps” are “bridgeable.” Still, the top US diplomat made clear his exasperation at both the changes Hamas proposed and the length of time it took to reply – 12 days. He did not go into specific details about the changes, but he continued to cast exclusive blame for the stalling of the deal – and the prolonging of the suffering of the Palestinians in Gaza – on the US-designated terrorist group, not on Israel.

“Israel accepted the proposal as it was,” he reiterated, despite repeated public statements from Israeli Prime Minister Benjamin Netanyahu seeming to cast doubt on his approval of the proposal.

“At some point in a negotiation – and this has gone back and forth for a long time – you get to a point where if one side continues to change its demands, including making demands and insisting on changes for things that it had already accepted, you have to question whether they’re proceeding in good faith or not,” Blinken said in reference to Hamas.

“It’s time for the haggling to stop and a ceasefire to start. It’s as simple as that,” he said.

While much of Blinken’s trip to Egypt, Israel, Jordan and Qatar had been centered on ratcheting up pressure on Hamas to take the proposal for an immediate ceasefire, it was also focused on developing plans for when a ceasefire is put into place.

It is “crucial” to move from an “immediate ceasefire” in Gaza “to an enduring end” to the war, Blinken said Wednesday in some of his most straight-forward comments yet calling for the end to the eight-month long conflict.

“In the coming weeks, we will put forward proposals for key elements of the ‘day after’ plan, including concrete ideas for how to manage governance, security, reconstruction,” the top US diplomat said, without providing further details.

Still, any movement on any of those aspects is contingent on an end to the fighting in Gaza, which has claimed the lives of more than 37,000 Palestinians and left the strip in what aid officials have described as an “unprecedented” humanitarian catastrophe.

“In the days ahead, we are going to continue to push on an urgent basis with our partners, with Qatar, with Egypt, to try to close this deal,” Blinken said Wednesday as he wrapped up his eighth round of shuttle diplomacy since the October 7 Hamas attack.

Hamas submitted its reply to the multi-phased ceasefire and hostage release proposal to mediators on Tuesday. According to a senior State Department official, Blinken, who was in Amman at the time, dispatched two of the senior staff traveling with him to retrieve Hamas’ response from Egyptian Intelligence Chief Abbas Kamel, who was also in the Jordanian capital.

Izzat al-Rishq, a member of the Hamas political bureau, described their response as “responsible, serious and positive.”

CNN’s Hamdi Alkhshali and Benjamin Brown contributed to this report.

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