The US is facing intense criticism for withdrawing its forces from Syria, which some say gave Turkey the green light to launch a cross-border offensive against Kurdish-led forces.
Mr Trump told reporters at the White House the US is “not a policing agent”.
“It is time for us to go home,” he said.
The US House of Representatives voted overwhelming to condemn the president’s withdrawal of US forces from Syria, with both Democrats and Mr Trump’s fellow Republicans approving the measure.
Speaker of the House Nancy Pelosi later told reporters Mr Trump had had a “meltdown” during a meeting with congressional leaders about Syria, which Democratic politicians eventually left after the president allegedly called her a “third-rate politician,” according to Democratic Senator Chuck Schumer.
For his part, Mr Trump aimed the same accusation at Ms Pelosi.
Turkey launched the offensive in northern Syria a week ago to push back from its border members of a Syrian Kurdish militia called the People’s Protection Units (YPG) and create a “safe zone” along the Syrian side of the border, where up to two million Syrian refugees can be resettled.
The Turkish operation came after Mr Trump ordered the withdrawal of US forces from the area.
Kurdish-led forces have been a key ally of the US in the fight against Islamic State in Syria and there are fears the destabilisation could lead to a resurgence of the militants.
What did the president say?
Earlier reports suggested the president said Turkey’s operation in Syria was “not our problem”. In fact, Mr Trump said: “They have a problem at a border. It’s not our border. We shouldn’t be losing lives over it.”
Mr Trump said he saw the situation on the Turkey-Syria border as “strategically brilliant” for the US.
“Our soldiers are out of there. Our soldiers are totally safe. They’ve got to work it out. Maybe they can do it without fighting,” he said.
“We’re watching and we’re negotiating and we’re trying to get Turkey to do the right thing, because we’d like to stop wars regardless.”