Ankara: The United States would prefer that Turkish troops “remove themselves” from a conflict in the Syrian border town of Afrin, President Donald Trump’s homeland security adviser said Thursday. He also appealed to President Recep Tayyip Erdogan to focus on “longer-term strategic goals” of a peaceable Syria.

Speaking at the World Economic Forum in Davos before Trump’s arrival later, Tom Bossert said Turkey “ought to be mindful of the potential for escalation as they move into Syria and Afrin.”

The United States has previously expressed concerns over Turkey’s military offensive against the Kurdish-controlled enclave of Afrin in northwest Syria but Bossert’s comments were the most direct call for Turkey to withdraw.

Turkish leaders have threatened to expand their drive against the Syrian Kurdish People’s Protection Units, or YPG, to other border areas, a move that could put Turkish troops in direct conflict with US forces and their Syrian Kurdish allies. US troops have no presence near or in Afrin, but there are a couple of thousands servicemen stationed farther east.

The United States relies on the YPG - which forms the backbone of a force that drove Daesh fighters from much of northeast Syria - to patrol areas taken from the extremist group. The YPG, backed by the US, now control 25 percent of Syrian territory. Turkey considers the YPG as an extension of outlawed Kurdish rebels fighting Ankara and a national security threat.

US support for the YPG has heightened tensions between the two countries, who are NATO allies.