Trump landed at 7:16 pm local time at Al-Asad Air Base in western Iraq, accompanied by his wife Melania Trump, an AFP correspondent said. The president spoke to troops and met with military leaders.

Although the visit took place in considerable secrecy, speculation had been mounting that Trump might make such a trip following his decision to slash troop levels in Afghanistan and pull out entirely from Syria.

"President Trump and the First Lady traveled to Iraq late on Christmas night to visit with our troops and Senior Military leadership to thank them for their service, their success, and their sacrifice and to wish them a Merry Christmas," White House spokeswoman Sarah Sanders tweeted.

Melania Trump's spokeswoman called it "a surprise visit to our brave U.S. service members currently deployed in Iraq."

Presidential trips to boost troop morale have been a longstanding tradition in the years of war following the September 11, 2001 terrorist attacks, and Trump has taken considerable criticism for declining until now to experience a war zone.

But apart from the photo ops alongside uniformed military members, Trump is expected to use the Iraq trip to further explain his decision to end the Syria deployment and cut troops in Afghanistan.

The policy changes, defended by Trump as an exit from wars where the United States no longer needs to be expending lives and money, have sparked alarm among US allies.