President Donald Trump on Friday set a Sunday deadline for Hamas to respond to his 20-point Gaza peace proposal, threatening that they would face “all HELL, like no one has ever seen before” if they reject the offer.

“We will have PEACE in the Middle East one way or the other,” Trump wrote in a social media post. “The violence and bloodshed will stop. RELEASES THE HOSTAGES, ALL OF THEM, INCLUDING THE BODIES OF THOSE THAT ARE DEAD, NOW! An Agreement must be reached with Hamas by Sunday Evening at SIX (6) P.M., Washington, D.C. time. Every Country has signed on! 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.”

Israeli Prime Minister Benjamin Netanyahu said on Monday during a visit at the White House that he supported Trump’s plan, which lays out conditions for a ceasefire, the exchange of hostages and prisoners and the establishment of an international trusteeship that would govern Gaza in the short-term. The plan also calls for Hamas to effectively surrender and disarm.

Initially, Trump and top aides said they were going to give Hamas “three or four days” to respond to the proposal. Qatar and other Arab allies have been in close contact with Hamas officials and urged the group’s leaders to accept the proposal, according to a person familiar with the matter who was granted anonymity because they weren’t authorized to speak publicly.