US President Donald Trump has given Hamas a deadline to accept a US peace plan for Gaza or face “all hell”.

Trump wrote on his Truth Social platform on Friday that an agreement must be reached by 18:00 Washington time (22:00 GMT) on Sunday.

The plan proposes an immediate end to fighting and the release within 72 hours of 20 living Israeli hostages held by Hamas – as well as the remains of hostages thought to be dead – in exchange for hundreds of detained Gazans.

Arab and Turkish mediators are understood to be pressing Hamas for a positive response to the proposal, but a senior Hamas figure has said the armed group is likely to reject it.

“If this LAST CHANCE agreement is not reached, all HELL, like no one has ever seen before, will break out against Hamas. THERE WILL BE PEACE IN THE MIDDLE EAST ONE WAY OR THE OTHER,” Trump wrote in the Truth Social post.

The deadline announced on Friday comes after Trump said on Tuesday that he was giving Hamas “three to four days” to respond to the peace plan.

Mediators have made contact with the head of Hamas’s military wing in Gaza, who has indicated he does not agree to the new US ceasefire plan, the BBC understands.

It is thought that some of Hamas’s political leadership in Qatar are open to accepting it with adjustments – but have found their influence limited as they do not have control of the hostages held by the group.

Another stumbling block for some in Hamas is that the plan requires them to hand over all of the hostages over the first 72 hours of the ceasefire – giving away their only bargaining chip.

There are believed to be 48 hostages still being held in the Palestinian territory by the armed group, only 20 of whom are thought to be alive.

In a briefing at the White House on Friday afternoon, Press Secretary Karoline Leavitt said that the consequences of turning down the deal would be “very grave” for Hamas.

“I think that the entire world should hear the president of the United States loud and clear,” Leavitt added. “Hamas has an opportunity to accept this plan and move forward in a peaceful and prosperous manner in the region. If they don’t, the consequences, unfortunately, are going to be very tragic.”

The 20-point plan, agreed by Trump and Israeli Prime Minister Benjamin Netanyahu and announced by both at the White House on Monday, also says Hamas will have no role in governing Gaza, and leaves the door open for an eventual Palestinian state.

However, Netanyahu later reinstated his longstanding opposition to a Palestinian state, saying in a video statement shortly after the announcement: “It’s not written in the agreement. We said we would strongly oppose a Palestinian state.”

The plan stipulates that once both sides agree to the proposal “full aid will be immediately sent into the Gaza Strip”.

It also outlines a plan for the future governance of Gaza, saying a “technocratic, apolitical Palestinian committee” will govern temporarily “with oversight and supervision by a new international transitional body, called the Board of Peace”, which it says will be headed by Trump.

European and Middle Eastern leaders have welcomed the proposal. The Palestinian Authority (PA), which governs parts of the Israeli-occupied West Bank, has called the US president’s efforts “sincere and determined”.

Pakistan initially voiced support for the plan, but the country’s foreign minister has since said the points announced were not in line with a draft from a group of Muslim-majority countries, BBC Urdu and Reuters reported.

Trump has said that if Hamas does not agree to the plan, Israel would have US backing to “finish the job of destroying the threat of Hamas”.

Netanyahu has also said Israel “will finish the job” if Hamas rejected the plan or did not follow through.

The Israeli military launched a campaign in Gaza in response to the Hamas-led attack on southern Israel on 7 October 2023, in which about 1,200 people were killed and 251 others were taken hostage.

At least 66,288 people have been killed in Israeli attacks in Gaza since then, according to the territory’s Hamas-run health ministry.

In the 24 hours before Friday midday, 63 people were killed by Israeli military operations, the health ministry said.

The push for the peace plan comes as Israel is carrying out an offensive in Gaza City, with Israel’s defence minister saying earlier this week that Israeli forces were “tightening the siege” around the city.

Israel has said the offensive aims to secure the release of the remaining hostages.

Hundreds of thousands of Gaza City residents have been forced to flee after the Israeli military ordered evacuations to a designated “humanitarian area” in the southern al-Mawasi area, but hundreds of thousands more are believed to have remained.

Israel’s defence minister has warned that those who stay during the offensive against Hamas would be “terrorists and supporters of terror”.

James Elder, spokesman for the UN children’s agency, Unicef, said on Friday that the idea of a safe zone in southern Gaza was “farcical”.

“Bombs are dropped from the sky with chilling predictability. Schools, which have been designated as temporary shelters, are regularly reduced to rubble,” he said.

(With additional reporting from Bernd Debusmann Jr at the White House)