He added: "If there's trouble, if somebody is looking to do nuclear weapons or other things, we're going to know it before they do".
USA military commanders rely heavily on Syrian forces to gather intelligence from information and material gathered from the battlefield, but also a wide-range of informers with firsthand knowledge about ISIS operations.
In an interview with CBS News, President Trump said "We've been there for 19 years, almost, we are fighting very well".
"So when my intelligence people tell me how wonderful Iran is - if you don't mind, I'm going to just go by my own counsel", he said. "The US is a major power. but do not pursue your own policy priorities".
Trump said that the USA troops in Syria were starting to come home, as they push out the "final remainder of the [IS] caliphate".
Trump also said he plans to transfer some of the American troops stationed in Syria to Iraq. He said the constitution forbids the use of Iraq as a base to threaten the interests or security of neighboring countries.
President Trump speaks at a hanger rally at al-Asad Air Base, Iraq, Wednesday, Dec. 26, 2018. But we didn't have Syria whereas we had Iraq.
Remembering Kristoff St. John on 'Young and the Restless'
Since first appearing on the show in 1991, the actor has won a Daytime Emmy and multiple NAACP Image Awards for his role. John played a young Alex Haley in the 1979 miniseries Roots: The Next Generations .
USA troops who stay in Iraq will also keep an eye on Syria, the president added. We might as well keep it. "And one of the reasons I want to keep it is because I want to be looking a little bit at Iran because Iran is a real problem", he said.
Trump did not meet any Iraqi officials during his three-hour long stay there.
Trump's comments appear to have further inflamed tensions in Iraq over the continued presence of US troops after the defeat of the Islamic State group.
This is not the first time the Iraqi government has expressed an unwillingness to host an estimated 5,200 American troops.
Iraqi politicians allied to Iran or the influential Shia cleric Moqtada Sadr, a long-time adversary of the USA who also opposes Iranian influence in Iraq, have for weeks been calling on the government to remove of all foreign troops from the country.
"If the USA is perceived as being in Iraq not exclusively to assist the Iraqi forces in [the] fight against ISIS, it will strengthen the hand of those who oppose the U.S. presence", said David Witty, a retired United States special forces colonel. "We're at 99 percent right now, we'll be at 100", Trump said. And I think that they will- I think they're exhausted and, I think everybody's exhausted.
The amendment acknowledged progress against Islamic State and al Qaeda in Syria and Afghanistan but warned that "a precipitous withdrawal" without effective efforts to secure gains could destabilize the region and create a vacuum that could be filled by Iran or Russian Federation.