ABU DHABI  - U.S. forces will stay in Iraq "as long as needed" to help stabilize regions previously controlled by Islamic State, a spokesman for the U.S.-led international coalition fighting the militants said on Sunday.

"We'll keep troops there as long as we think they're needed ... The main reason, after ISIS (Islamic State) is defeated militarily, is the stabilization efforts and we still need to be there for that, so that's one of the reasons we'll maintain a presence," Colonel Sean Ryan told a news conference in Abu Dhabi.

The number of American soldiers could go down however, depending on when other forces from the North Atlantic Treaty Organisation deploy to help train the Iraqi army, he said, adding that about 5,200 U.S. troops are currently based in Iraq.

NATO defence ministers agreed in February to a bigger "train-and-advise" mission in Iraq after a U.S. call for the alliance to help stabilise the country after three years of war against Islamic State. 

"Possibly, there could be a drawdown, it just depends on when NATO comes in and they help train the forces as well," Ryan said.

Iraq officially announced victory over the militants in December, five months after capturing their stronghold Mosul.

The United States also has about 2,000 troops in Syria, assisting the Kurdish-led Syrian Democratic Forces (SDF) clear pockets still under the control of Islamic State along the border with Iraq.

"We're starting to see a lot of collaboration between the SDF and ISF (Iraqi Security Forces) because it used to be that they would just come to the coalition, but now, we have them talking to each other as well," said Ryan.

The Iraqi military has carried out several air strikes against Islamic State in Syria since last year, the last of which a few days ago, with the approval of President Bashar al-Assad and the U.S.-led coalition.

SDF operations to finish off the militants on the Syrian side have been delayed by hundreds of explosive devices planted by Islamic State, according to Ryan.

(Reporting Tuqa Khalid; Writing by Maher Chmaytelli; Editing by Mark Heinrich) ((maher.chmaytelli@thomsonreuters.com; +9647901917030;))