FILE PHOTO - U.S army soldiers walk at the Qayyarah West Airfield, Iraq March 1, 2017. REUTERS/Azad Lashkari

BAGHDAD (Reuters) - U.S. forces have begun reducing their numbers in Iraq after Iraqi authorities declared victory over Islamic State, an Iraqi government spokesman said on Monday.

Iraqi forces backed by a U.S.-led international coalition last year captured all the territory that fell under Islamic State control in 2014 and 2015, including the northern city of Mosul, which served as the militants’ de facto capital.

“The American forces have begun reducing their numbers as victory has been achieved over Daesh,” the spokesman told Reuters, referring to the Islamic State militant group.

“Coordination continues, to maintain (U.S.) assistance to the Iraqi forces in accordance with their requirements.”

The United States is believed to have around 7,000 troops in Iraq, even though the Pentagon has only acknowledged 5,200 troops. The troops have been mostly training and advising Iraqi forces.

In a statement, the coalition said it would “shift its focus in Iraq from enabling combat operations to sustaining military gains against” Islamic State militants.

“The Coalition will tailor our forces in consultation with our Iraqi partners in order to ensure the lasting defeat of Daesh,” the director of operations for the coalition, Brigadier General Jonathan Braga, said.

Braga said that even if the composition of the force changes, the coalition would maintain the capabilities and presence to continue to train, advise and equip Iraqi forces to ensure that Islamic State does not re-emerge.

U.S. officials say that while Islamic State has lost most of the territory it once controlled in Iraq and Syria, there is concern about the remaining fighters returning to insurgency tactics.