The ceasefire between Hamas and Israel appeared increasingly fragile Tuesday after US President Donald Trump warned "all hell" would break loose unless Hamas releases every Israeli hostage by the weekend.

The truce, in place since January 19, largely halted more than 15 months of fighting in the Gaza Strip and saw five groups of Israeli hostages freed in exchange for hundreds of Palestinian prisoners.

But tensions spiked after Trump proposed taking over Gaza and removing its more than two million inhabitants.

On Monday, he ramped up pressure, saying he would call for an end to the ceasefire if all Israeli hostages were not freed by noon on Saturday.

"As far as I'm concerned, if all of the hostages aren't returned by Saturday 12 o'clock -- I think it's an appropriate time -- I would say cancel it and all bets are off and let hell break out," Trump told reporters at the White House.

The ceasefire agreement says staggered releases should take place over the ongoing 42-day first phase of the deal.

Trump's threat came hours after Hamas's armed wing, the Ezzedine al-Qassam Brigades, said the next hostage release due to take place on Saturday would be "postponed until further notice".

The group accused Israel of failing to meet its commitments under the agreement, including on aid deliveries, and cited the deaths of three Gazans on Sunday.

Hamas later said it announced the delay five days in advance to give mediators time to push Israel to comply.

"The door remains open for the prisoner exchange batch to proceed as planned, once the occupation complies," it said.

'Complete violation'

Israeli Defence Minister Israel Katz said the Hamas announcement was a "complete violation" of the ceasefire agreement, signalling that fighting could resume.

"I have instructed the IDF (military) to prepare at the highest level of alert for any possible scenario in Gaza," he said.

The military later said it had raised "the level of readiness" around Gaza, and "decided to significantly reinforce the area".

On Tuesday, Israeli far-right Finance Minister Bezalel Smotrich, a fierce opponent of the ceasefire, demanded the immediate release of all hostages, adopting the slogan: "Everyone Now."

Negotiators were set to meet in Qatar to discuss the truce's implementation, which remain unsettled.

Talks on a second phase were supposed to start on day 16 of the truce, but Israel had refused to send its negotiators to Doha.

The Hostage and Missing Families Forum campaign group said on Monday it had "requested assistance from the mediating countries to help restore and implement the existing deal effectively".

Trump on Jordan, Egypt

On Sunday, Israeli Prime Minister Benjamin Netanyahu praised Trump's proposal to displace Gazans as "revolutionary", striking a triumphant tone after returning from Washington.

The proposal, which the United Nations and experts have said would violate international law, has already drawn widespread criticism.

Trump said Monday he could "conceivably" halt aid to US allies Jordan and Egypt if they refuse to take in Palestinians under his controversial Gaza plan.

Trump is due to meet Jordan's King Abdullah II in Washington this week.

The threat to withhold aid came after Cairo's foreign ministry said it rejected "any compromise" of Palestinian rights, including "remaining on the land".

Trump told Fox News Channel's Bret Baier earlier Monday that Palestinians would not have the right to return to Gaza.

"I'm talking about building a permanent place for them because if they have to return now, it'll be years before you could ever -- it's not habitable," said Trump of devastated Gaza.

Asked if the Palestinians would have the right to return, Trump said: "No, they wouldn't, because they're going to have much better housing."

For Palestinians, any attempt to force them out of Gaza would evoke dark memories of what the Arab world calls the "Nakba" or catastrophe -- the mass displacement of Palestinians during Israel's creation in 1948.

Despite Trump's words, displaced Gazans streamed back to their homes after Israeli forces withdrew from the Netzarim Corridor that cut the territory in two.

US and Egyptian security personnel were on the ground inspecting vehicles crossing the corridor.

Gaza resident Ahmed al-Rai said "it takes 20 minutes to inspect each vehicle" and that he had to wait five hours for his turn.

The Gaza war was triggered by Hamas's October 7, 2023 attack, the deadliest in Israel's history, which resulted in the deaths of 1,210 people, mostly civilians, according to an AFP tally of official Israeli figures.

Militants also took 251 hostages, of whom 73 remain in Gaza, including 34 the Israeli military says are dead.

The health ministry in Hamas-run Gaza says the war has killed at least 48,208 people in the territory.

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