Prime Minister Benjamin Netanyahu said Thursday that a last-minute dispute with Hamas was holding up Israeli approval of a long-awaited ceasefire that would pause the fighting in the Gaza Strip and release dozens of hostages.

The delay raised concerns about the implementation of the deal, scheduled to go into effect on Sunday, shortly after President Joe Biden and key mediator Qatar announced it was complete.

Multiple officials announced Wednesday that Israel and Hamas agreed to a ceasefire deal to pause the devastating war in the Gaza Strip, raising the possibility of winding down the deadliest and most destructive fighting between the bitter enemies.

The prime minister of Qatar, Sheikh Mohammed bin Abdulrahman Al Thani, said the ceasefire would go into effect on Sunday. He made the announcement in the Qatari capital of Doha, the site of weeks of painstaking negotiations.

Biden then touted the deal from Washington, saying the ceasefire will stay in place as long as Israel and Hamas remain at the negotiating table over a long-term truce. Biden said his administration and President-elect Donald Trump’s team were “speaking as one” in the negotiations.

An Israeli official familiar with the talks who spoke on condition of anonymity said those details center on confirming the list of Palestinian prisoners who are to be freed. Any agreement must be approved by Netanyahu’s Cabinet.

Once the deal officially begins, it is expected to deliver an initial six-week halt to fighting that is to be accompanied by the opening of negotiations on ending the war altogether.