And Trump defended his controversial decision to pull US troops out of neighboring Syria, saying there would be no delays.

"You can't have any more time. You've had enough time," he said he had told his generals.

This was Trump's first visit to US combat troops in the two years since his election. It came as he faces strong pushback from some allies, including France, and from some of his own Republican party members on his decision to exit Syria and to slash troop numbers in Afghanistan.

Critics say he is being dangerously hasty.

But Trump stressed during his brief stop at Al-Asad Air Base in western Iraq that the United States has been fighting other countries' battles for them for too long.

"It's not fair when the burden is all on us," he said. "We don't want to be taken advantage of any more by countries that use us and use our incredible military to protect them. They don't pay for it and they're going to have to."

"We are spread out all over the world. We are in countries most people haven't even heard about. Frankly, it's ridiculous," he added.