Trump did not provide a timetable for the planned military exit from Syria, which he unexpectedly announced last month against the advice of top national security aides and without consulting politicians or U.S. allies participating in the fight against the Islamic State of Iraq and the Levant (ISIL, also known as ISIS).
Much of the criticism surrounding the President's decision to withdraw troops from Syria - a move he frequently mentioned both on the campaign trail and in office - has been tied to the possibility that a lack of United States troops could allow ISIS to regain some of its strength in the region.
President Donald Trump tweeted early Monday morning that any other president would be praised for eliminating ISIS and bringing troops back home from overseas, but that he faces criticism for doing exactly that.
On Iran, Mr Trump praised his own strategy, saying that the sanctions have worked and turned it into a different country.
Mattis announced his resignation in a searing letter just before Christmas that highlighted his differences with the president over the role of American leadership and alliances. Trump, in his December 19 pullout announcement, cited the same reasons, arguing that troops had no need to stay in the war-torn country.
He said: "I shouldn't be popular in Europe". We have other bases in the general area.
The US has at least 2,000 troops stationed in the region, where it has also waged an aerial campaign in support of the Kurdish-led Syrian Democratic Forces (SDF) in the fight against the Islamic State (IS) group.
Though much reduced, and forced into hiding, it is still believed to comprise thousands of guerrillas.More news: Democratic Senator Warren takes step toward 2020 US presidential bid
The official, speaking on condition of anonymity to reporters in Rio de Janeiro as Netanyahu continues his state visit to Brazil, said the premier made the request during a recent phone call with Trump, after the USA leader announced plans to remove troops from the war-torn Arab country. US-backed forces seized the jihadists' self-declared capital Raqa on Oct 17, 2017.
Part of Trump's appeal in his surprise 2016 election victory was his promise to get the United States out of post-9/11 wars in the Middle East.
While White House officials have denied reports that Trump also has ordered half of the 14,000 U.S. troops in Afghanistan to come home, Trump made it clear he has run out of patience for what's become the longest USA war. "Look, we don't want Syria". "They can do what they want there, frankly, but they're pulling people out", he added.
The view is popular with many Americans, but critics, including some of Washington's closest allies, say the United States can not abandon its traditional leadership role.
Graham emerged after two hours, saying Trump "understands the need to finish the job".
"I think we're in a pause situation", the South Carolina Republican said outside the White House after lunch with the president.
Another prominent critic of the pullout was retired USA army general Stanley McChrystal, the former commander of United States and worldwide forces in Afghanistan, who on Sunday warned on ABC's "This Week" that a U.S. pullout would likely cause "greater instability" in the region.