Trump told reporters as he departed the White House that Israeli and Arab leaders had accepted the plan and "we're just waiting for Hamas".
He said Hamas has about "three or four days" to respond.
"Hamas is either going to be doing it or not, and if it's not, it's going to be a very sad end," he said.
Asked if there was room for negotiations on the peace plan, Trump said: "Not much."
Qatari and Egyptian officials have presented the 20-point proposal to Hamas negotiators, who are reviewing it.
At least 27 Palestinians were killed in the Gaza Strip on Tuesday, local hospitals said.
In Netzarim, the Israeli-controlled corridor that bisects the north and south of the enclave, 17 Palestinians were killed and 33 wounded while attempting to access humanitarian aid, al-Awda hospital said.
Separately, at least two Israeli strikes on tents in the region of Muwasi, previously deemed a safe zone by the Israeli military, killed 10 people, two hospitals reported.
The Israeli military did not immediately comment on the shooting or strikes, saying its troops had killed several armed militants and struck more than 160 targets of Hamas infrastructure in the past 24 hours.
Israeli Foreign Minister Gideon Saar said that his country has accepted Trump's "plan for ending the war in Gaza and for a better future" and that it was now up to Hamas to announce its position.
"We will now see if Hamas accepts the president's plan," Saar said during a visit to Serbia.
He accused Hamas of trying in the past to change the terms or avoid implementing any past agreements.
"We will see," he said.
with AP
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