"Big election tomorrow in Israel," Trump told reporters at the White House.
"It's going to be close... it's a 50/50 election."
Israel is holding its second election in five months on Tuesday, with Prime Minister Benjamin Netanyahu battling for his political survival.
Netanyahu, Israel's longest-serving prime minister, suffered one of the biggest defeats of his career after April elections, when he failed to form a coalition despite his right-wing Likud and its allies winning a majority of seats.
Rather than risk having Israeli President Reuven Rivlin choose someone else to form a government, Netanyahu, who could be indicted on corruption charges in the coming weeks, opted for a second election instead.
Final opinion polls released Friday indicated another tight race between Likud and the centrist Blue and White alliance led by ex-military chief Benny Gantz, and a repeat stalemate cannot be ruled out.
The poll is expected to once again amount largely to a referendum on Netanyahu.