"I had a call today with Prime Minister Netanyahu to discuss the possibility of moving forward with a Mutual Defense Treaty, between the United States and Israel," Trump tweeted.
He said such an agreement would "further anchor the tremendous alliance" between the two countries.
"I look forward to continuing those discussions after the Israeli Elections when we meet at the United Nations later this month!" Trump added, giving a tacit last-minute endorsement to Netanyahu's re-election bid.
The comments come as the international community awaits the release of Washington's long-delayed Middle East peace plan, which Secretary of State Mike Pompeo recently said could come within weeks.
Its publication was pushed back after Israel scheduled new elections, set for Tuesday.
Then last week, one of the key architects of the US plan, Jason Greenblatt, announced his resignation.
Trump has repeatedly boasted that he is the most pro-Israeli US president in history. He has slashed aid to the Palestinians, while making big concessions to the Israelis, including formalizing US recognition of Jerusalem as the capital of the Jewish state.
As a result, the Palestinian Authority has cut off formal contact with the Trump administration, saying it is not an honest broker.
So far, Trump has not commented on Netanyahu's controversial pledge to annex Israeli settlements in the occupied West Bank as well as the Jordan Valley if re-elected -- which would seem to go beyond US proposals for land swaps between Israel and the Palestinians.
Netanyahu, 69, is fighting his second election in five months with a potential corruption indictment looming. He suffered a major defeat in April, when his Likud party along with its right-wing and religious allies won a majority, but he failed to form a coalition.