The comment came a day after what Trump called a "major milestone" towards ending the war in the enclave that he said would result in the complete disarmament of Hamas and other armed groups.
"It's a big step for the Middle East, and people are really impressed by it, and they're surprised by it," he said.
Trump's announcement on Thursday of the agreement by his "Board of Peace" followed months of faltering efforts to keep the ceasefire agreement reached last year in the Egyptian resort of Sharm el-Sheikh on track and it was not immediately clear how strongly either Hamas or Israel stood behind it.
Previous attempts to reach an accord have foundered amid mutual suspicion and each side's insistence that the other must move first.
A senior Hamas official involved in the negotiation told Reuters that implementation of the deal would depend on Israel first meeting its commitments under an agreement reached last year that bound it to a phased end to military operations and withdrawal of its forces from the Gaza Strip.
An Israeli official said Israel's position remained that "there will be no withdrawal whatsoever of the IDF from the current Yellow Line unless Hamas undergoes a genuine disarmament," referring to a military demarcation line agreed in the ceasefire.
Trump, who met Israeli Prime Minister Benjamin Netanyahu in Washington DC on Tuesday, said Israel was "very happy" about the deal.
"Israel helped us, and they've been very good," he said.
"Will it go through its ups and downs? It's a very complex situation over there."
An Israeli political source said on Thursday the issue of the Gaza Strip did not come up during Netanyahu's meeting with Trump.
On Friday, Hamas issued a statement saying the first step towards an agreement would have to be a commitment by Israel "to stopping the killing and ending its attacks".
But within hours of Trump unveiling the deal, Gazan medical authorities said one Palestinian was killed and several others had been wounded in at least two Israeli air strikes and by gunfire in the enclave.
The Israeli military said it was reviewing one incident in which a strike intended to hit a member of Hamas' armed wing was diverted after uninvolved individuals were identified.
It said it was unaware of the shooting.
Netanyahu, who faces an election in October in which he is likely to rely on support from coalition partners, has so far not commented officially.
But Police Minister Itamar Ben-Gvir, head of the ultranationalist Jewish Power party, said on his Telegram channel that the draft agreement was unacceptable and that Israel's policy of assassinating Hamas leaders must continue.
Ghazi Hamad, a Hamas official involved in the negotiations, told Reuters the group was ready to accept an agreement he said was "difficult and painful".
But he avoided using the term disarmament and said the agreement was a "comprehensive framework" that would depend on Israel implementing the first phase of the Sharm el-Sheikh agreement.
Under that agreement, he said Israel was obliged to end its attacks in the Gaza Strip and withdraw its forces to where they stood in October, as well as increase the flow of goods and aid coming into the enclave.
Only then would Hamas agree to hand over its weapons for storage by the new National Committee for the Administration of Gaza, the Palestinian technocratic body set up to run the enclave.
