Trump's decision to call back USA troops in Syria, who were first deployed in 2015, was followed a day later by the resignation of Defense Secretary Jim Mattis, who wrote a letter to the president saying he had the right to have a secretary of defense "whose views are better aligned with yours".
"Out of concern for operational security, we will not discuss specific timelines, locations or troop movements", Ryan said.
The Syrian Democratic Forces (SDF), a coalition of militias led by the Kurdish YPG, have driven Islamic State from a swathe of northern and eastern Syria with the help of the USA -led coalition over the last four years.
Ankara believes that the Syrian Kurds - who have been allies to the U.S.in the fight against ISIS - are linked to groups that are trying to destabilize Turkey. National Security Advisor John Bolton even said that USA forces will not leave Syria until Turkey guarantees the safety of the US-backed Kurdish militias.
Relations between the two North Atlantic Treaty Organisation allies have been strained over USA backing for the Kurdish YPG, which Turkey views as an extension of the outlawed Kurdistan Workers Party (PKK) waging a decades-long insurgency on Turkish soil.
Senior U.S. officials and lawmakers have called on Trump to not abandon the PYD/YPG as he pulls out of Syria.
But, he added, "we also know that those fighting alongside of us for all this time deserve to be protected as well".
Efforts to destroy IS in Syria have been dominated by the Syrian Democratic Forces, whose members are mostly Kurds.
US President Donald Trump on Sunday (local time) threatened to "devastate Turkey economically" if it attacked the Kurds in the region. That drew a rebuke from Turkish President Tayyip Erdogan who called his comments "a serious mistake".
He said: "Terrorists can't be your partners and allies".
The Kurds are looking for protection against a possible Turkish attack and Syria's Assistant Foreign Minister Ayman Sousan told reporters Sunday his government would like an intensified dialogue with the Kurds.
Washington, however, considers the group as an effective force in the fight against IS.
Turkey has criticized the US working with the terrorist PKK/PYD to fight Daesh, saying that using one terror group to fight another makes no sense.
Nor will it stop the United States from trying to get "every Iranian boot out of Syria", Pompeo said.
A Kurdish politician told Reuters last week the Kurds had presented Moscow with a roadmap for a deal with Damascus.
Special representative for Syria Jim Jeffrey, a former US envoy to Turkey and Iraq, is expected to return to Turkey to continue discussions, Pompeo added.