U.S. President Donald Trump talks to Turkey’s President Recep Tayyip Erdogan at NATO headquarters in Brussels, Belgium July 11, 2018. Tatyana Zenkovich/Pool via REUTERS

ISTANBUL (Reuters) - Turkish President Tayyip Erdogan and U.S. President Donald Trump discussed Manbij and Idlib in northern Syria in a call on Thursday and stressed their determination to strengthen ties, Erdogan’s office said.

Turkish and U.S. forces began joint patrols on Thursday in the Manbij region, a source of friction in recent years after Kurdish forces took part of the area in a U.S.-backed offensive to drive out Islamic State in 2016.

“Our President and U.S. President Trump stressed their determination to take constructive steps toward strengthening U.S.-Turkey bilateral relations further,” the statement said, while also referring to developments in Syria’s Idlib region.

White House spokeswoman Sarah Sanders confirmed the call, saying the two leaders discussed a desire to work together, especially regarding Syria.

Turkey, which has long backed rebels seeking to overthrow Syrian President Bashar al-Assad, and Russia, Assad’s principal foreign ally, brokered a deal in September to create a demilitarized zone in Idlib.

U.S.-Turkish relations have been strained by disputes over Syria, Iran and Ankara’s planned purchase of Russian military equipment. Prospects of improving ties rose last month after a Turkish court freed a U.S. pastor from two years of detention.