Less than a week into Turkey’s military operation in Afrin, Washington is exerting pressure on Ankara to de-escalate its activities amidst heightened US concerns the fighting is hurting the broader battle against ISIL in Syria.

US President Donald Trump stepped up his role on Wednesday, holding a lengthy phone conversation with his Turkish counterpart Recep Tayyip Erdogan . According to the White House, Mr Trump “relayed concerns that escalating violence in Afrin risks undercutting our shared goals in Syria”.

So far, at least 24 civilians have been killed, a figure Washington fears will increase if the fighting moves to the city centre.

Mr Trump urged “Turkey to de-escalate, limit its military actions, and avoid civilian casualties and increases to displaced persons and refugees” as well as to “exercise caution and to avoid any actions that might risk conflict between Turkish and American forces”. While US forces are not officially stationed in Afrin, they do have a presence 97km away in Manbij.

With increasing concerns from the US military that the fighting could distract Kurdish forces from the war against ISIL, Mr Trump urged that “both nations must focus all parties on the shared goal of achieving the lasting defeat of ISIL”.

In its statement, the White House said Mr Trump “invited closer bilateral co-operation to address Turkey’s legitimate security concerns” in fighting the YPG and the PKK. High-level Western sources told The National that Turkey only informed Washington of the Afrin operation "after the US government learned from a third party".

This left a bitter taste in US military and diplomatic quarters, and sped up attempts to improve co-ordination, with US defense secretary James Mattis emphasising that “top level” engagement is happening between the two sides.

The White House referred to the Kurdistan Workers’ Party (PKK) as a terrorist organisation, a gesture that will please Ankara. It called for “regional stability and combating terrorism in all its forms”, including ISIL, Al Qaeda, Iranian-sponsored terrorism and the PKK.

The National has also learned that a US delegation is visiting Turkey at the moment in a trip that was planned before the Afrin operation. It includes Jonathan Cohen, Deputy Assistant Secretary for European and Eurasian Affairs at the State Department, and Thomas Goffus, Deputy Assistant Secretary for European and NATO Policy at the Department of Defence. The delegation is meeting Turkish military generals and senior foreign policy officials.