Trump was responding to Hamas saying it will delay the further release of hostages in the Gaza Strip after accusing Israel of violating the three-week-old ceasefire. The U.S. president said that after the freeing of three visibly emaciated hostages on Saturday it was time for Israel to demand the release of all hostages by noon on Saturday, or restart the war.

“If they’re not here, all hell is going to break out,” Trump said. He added of the ceasefire, “Cancel it, and all bets are off.”

Trump said the final decision would be up to Israel, saying, “I’m speaking for myself. Israel can override it.” But asked if the U.S. would join in a response to Hamas if hostages weren’t freed, Trump added, “Hamas will find out what I mean.”

Those comments came after Trump said in an interview with Fox News Channel that Palestinians in Gaza would not have a right to return under his plan for U.S. “ownership” of the war-torn territory — contradicting other officials in his administration who have sought to argue Trump was only calling for the temporary relocation of its population.

Less than a week after he floated his plan for the U.S. to take control of Gaza and turn it into “the Riviera of the Middle East,” Trump, in an interview with Fox News’ Bret Baier airing Monday, said “No, they wouldn’t” when asked if Palestinians in Gaza would have a right to return to the territory. It comes as he has ramped up pressure on Arab states, especially U.S. allies Jordan and Egypt, to take in Palestinians from Gaza, who claim the territory as part of a future homeland.

“We’ll build safe communities, a little bit away from where they are, where all of this danger is,” Trump said. “In the meantime, I would own this. Think of it as a real estate development for the future. It would be a beautiful piece of land. No big money spent.”

Arab nations have sharply criticized the Trump proposal, and Trump is set to host Jordan’s King Abdullah II at the White House on Tuesday. In addition to concerns about jeopardizing the long-held goals of a two-state solution to the Israel-Palestinian conflict, Egypt and Jordan have privately raised security concerns about welcoming large numbers of additional refugees into their countries even temporarily.

When asked how he’d convince Abdullah to take in Palestinians, Trump told reporters, “I do think he’ll take, and I think other countries will take also. They have good hearts.”

But he also threatened to potentially withhold billions of dollars of U.S. assistance to Jordan and Egypt if they don’t go along with his plan.

“Yeah, maybe, sure why not,” Trump said. “If they don’t, I would conceivably withhold aid, yes.”

Trump’s comments risked jeopardizing the already tenuous ceasefire between Israel and Hamas in Gaza after 15 months of war, with the existing framework for negotiations calling for the massive humanitarian and reconstruction assistance for civilians in Gaza.

After Trump’s initial comments last week, White House press secretary Karoline Leavitt and Secretary of State Marco Rubio respectfully insisted that Trump only wanted Palestinians relocated from Gaza “temporarily” and for an “interim” period to allow for debris removal, the disposal of unexploded ordnance and reconstruction.

Speaking of the condition of the remaining hostages, Trump told reporters Monday that he feared Hamas had released the hostages in the best condition and that many scheduled for release are gravely ill or already dead. “Based on what I saw over the past two days, they’re not going to be alive for long,” he said.

In a video message released Saturday after Hamas freed the latest hostages on Saturday, Rachel and Jon Goldberg-Polin, the parents of slain American hostage Hersh Goldberg-Polin, called on Trump and his negotiating team to “think bigger and faster” and press for the release of all the remaining hostages this week.

“All 76 hostages out this week,” they said. “End of war. Who benefits from dragging it out for so long? Not the people of this region. Let’s get it done right now.”

Trump last week didn’t rule out deploying U.S. troops to help secure Gaza but at the same time insisted no U.S. funds would go to pay for the reconstruction of the territory, raising fundamental questions about the nature of his plan.

Egypt on Monday reiterated its rejection to the transfer of Palestinians from their territories in Gaza and the occupied West Bank, warning that such proposals threaten “the foundations of people” in the Middle East.

In a statement, the Egyptian Foreign Ministry said the establishment of an independent Palestinian state with East Jerusalem its capital is the base for “comprehensive and just peace” in the region.

The statement said Egypt rejects any violations to the Palestinians’ “right of self-determination … and independence,” and “upholds the right of return for Palestinian refugees who were forced to leave their homeland,” in a reference to hundreds of thousands who were forced to flee their homes in what is now Israel during the 1948 war.

A senior Hamas official blasted Trump’s latest remarks about the U.S. ownership of Gaza as “absurd.”

Izzat al-Rishq, a member of Hamas’ politico bureau, said these comments “reflect a deep ignorance of Palestine and the region.”

In comments released by Hamas early Monday, he said Trump’s approach toward the Palestinian cause will fail.

“Dealing with the Palestinian cause with the mentality of a real estate dealer is a recipe for failure,” he said. “Our Palestinian people will thwart all transfer and deportation plans.”