Qatar will stop trying to mediate a Gaza ceasefire and hostage release deal until Hamas and Israel show a “sincere willingness” to return to the negotiating table, an official briefed on the matter told Reuters on Saturday, in the biggest setback to efforts to reach a truce since the war began.

The small but influential Gulf country has also concluded that Hamas’ political office in Doha “no longer serves its purpose”, the official added, in a further blow to the Palestinian militant group whose top leaders have been assassinated by Israel.

Qatar, alongside the United States and Egypt, has played a major role in rounds of so-far fruitless talks to broker a ceasefire to the year-long war in Gaza and the release of Israeli hostages Hamas is holding in the enclave. The latest round of talks in mid-October failed to produce a deal, with Hamas rejecting a short-term ceasefire proposal.

“The Qataris have said since the start of the conflict that they can only mediate when both parties demonstrate a genuine interest in finding a resolution,” the official said.

Qatar has not set a deadline for Hamas’ political office to close or for Hamas leaders to leave Qatar and it was unclear if the move could be reversed.

Qatar informed Hamas, Israel and the US administration that it would be willing to resume its negotiating role if Hamas and Israel “demonstrate a sincere willingness to return to the negotiation table with the objective of putting an end to the war,” the official said.

There was no official response from Hamas.

A Palestinian official close to the mediation talks said: “Hamas may not comment unless it is informed officially by Qatar. So far it is media talk.”

Washington had told Qatar that Hamas’ presence in Doha was no longer acceptable in the weeks since the group rejected the latest proposal to achieve a ceasefire and a hostage deal, a US official said on Friday.

Qatar's government reconsidered Hamas’ presence in the country in April, which the official said prompted the group's leaders to leave for Turkey.

“After two weeks, the Biden administration and the Israeli government asked Qatar to request their return,” the official said, adding that Washington has said negotiations were ineffective when the Hamas leaders were in Turkey.

Qatar, designated as a major non-NATO ally by Washington, has hosted Hamas' political leaders since 2012 as part of an agreement with the US.

It is unclear how many Hamas officials live in Doha, but they include several touted as possible replacements for leader Yahya Sinwar, whom Israeli forces killed in Gaza last month, including Sinwar’s deputy Khalil al-Hayya, who has led ceasefire negotiations for the group, and Khaled Meshaal, widely seen as Hamas' diplomatic face.

The group’s previous leader Ismail Haniyeh, who was assassinated in Iran in July almost certainly by Israel, was also based in Doha. His body was flown to Qatar for burial in early August.