AL ASAD AIR BASE (Iraq) • United States President Donald Trump visited American military forces in Iraq, making his first trip to troops stationed in a combat zone only days after announcing his intention to withdraw the US from foreign wars in Syria and Afghanistan.

The trip on Wednesday, shrouded in secrecy, came during a partial government shutdown and less than a week after Mr Trump disrupted the military status quo and infuriated even some of his political allies by announcing plans to withdraw all troops from Syria and about half from Afghanistan.

The President's decision on Syria led to the resignation of Defence Secretary James Mattis.

Speaking to troops at Al Asad Air Base, Mr Trump defended his move in Syria. "We are no longer the suckers, folks," he said, adding: "Our presence in Syria was not open-ended, and it was never intended to be permanent. Eight years ago, we went there for three months, and we never left."

Mr Trump, who visited the air base with his wife Melania, said he had rejected requests from military commanders to remain in Syria for another six months. "I said, 'Nope. Nope.' I said, 'I gave you a lot of six months,' " the President said. "And now we are doing it a different way."

He told reporters that the US might base American commandos on the border in Iraq to launch raids and other missions into Syria.

Visiting troops abroad is a presidential tradition. Mr George W. Bush served Thanksgiving turkey to the soldiers in Baghdad in 2003, in the early days of the Iraq war.

Mr Barack Obama flew to Baghdad in April 2009 and won cheers when he told the troops that it was time for the Iraqis to take responsibility for their own country. He also visited Afghanistan four times while in office.

But nearly two years into his presidency, Mr Trump had yet to visit any troops abroad, drawing criticism from various corners. After he cancelled a visit last month to a US cemetery outside Paris during a World War I battlefield commemoration, Mr Trump said he had not visited troops abroad because of "an unbelievably busy schedule".

But on Wednesday, about 100 US servicemen and women, some of whom were wearing red "Make America Great Again" caps, greeted him with a standing ovation in Al Asad Air Base's dining facility, which had been decorated for Christmas.

Mr Trump ran for the presidency in 2016 on a platform of bringing the troops home from Afghanistan and Syria. It was part of a broader strategy of ending nearly two decades of American military interventions - including in Iraq, Libya, Syria and Afghanistan - that he criticised as costly, ineffective and at odds with his "America First" foreign policy.

But the US still has 14,000 troops in Afghanistan and about 2,000 in Syria.

While the number of casualties in these conflicts is a fraction of what it was during the two previous administrations, the fact that US troops are still on the ground - in the case of Afghanistan, 17 years after they were first deployed - attests to the difficulty of extracting the US from these entanglements.

Mr Trump, who was also accompanied to Iraq by National Security Adviser John Bolton, said that "the US cannot continue to be the policeman of the world".

The President's trip came at a moment of tension with some of his top military officials, and as his announcements on Afghanistan and Syria have left a trail of confusion.

He tried to dismiss those concerns while in Iraq, saying that "there will be a strong, deliberate and orderly withdrawal of US forces from Syria", and that having troops in Iraq would "prevent an ISIS (Islamic State in Iraq and Syria) resurgence".

"We can hit them so fast and so hard, they really won't know what the hell happened," he said.

Mr Trump spoke on the phone with Iraqi Prime Minister Adil Abdul-Mahdi and invited him to visit the White House, and the Prime Minister accepted.

But the President's trip was not universally applauded among members of the Iraqi Parliament.

"America has had a negative impact on Iraq through its interventions," said Mr Ghayib al-Amayri, a member of a powerful parliamentary alliance aligned with nationalist Shi'ite cleric Muqtada al-Sadr. "We are against the policy of Trump and against any intervention in Iraqi affairs."

After the visit in Iraq, the President headed to Germany, where he and the First Lady met service members early yesterday morning at Ramstein Air Base.