Mr Trump abruptly announced the USA withdrawal from Syria on December 19, blindsiding U.S. allies and triggering a confrontation within the United States administration that led to the resignation of his defence secretary.
Now, America's allies on the ground are turning to Washington's rivals for protection.
The top US diplomat said he was "optimistic" that Kurds who fought alongside USA forces against the Islamic State group in Syria are not threatened by pledges from Turkey's President Recep Tayyip Erdogan to launch military operations against what he terms Kurdish "terrorists".
"It is important that we do everything we can to make sure that those folks that fought with us are protected and Erdogan has made commitments, he understands that", Pompeo said during a Wednesday visit to the Kurdistan Region capital Erbil. The comments drew a rebuke from Erdogan, who slammed them as a "serious mistake". But in coming weeks, the contingent of about 2,000 troops is expected to depart even as the White House vows to keep pressure on the Islamic State group.
Top U.S. officials were shocked too, including Defense Secretary Jim Mattis, who quit in protest.
Uncertainty over the timing and terms of the Syria pullout have raised questions about the Trump administration's broader strategy for fighting Islamic extremism, including Trump's stated intention to reduce USA forces in Afghanistan this summer.
After announcing the pullout, Trump tweeted that Turkey's Recep Tayyip Erdogan "has very strongly informed me that he will eradicate whatever is left of (the Islamic State) in Syria", adding that the Turkish strongman was "a man who can do it".
Trump's decision to withdraw troops has been clouded by mixed messages from Washington since it was abruptly announced last month, catching off guard allies including the Kurdish-led Syrian Democratic Forces militia.
Seeking to quell concern about the US troop withdrawal from Syria, Secretary of State Mike Pompeo on Saturday described the American exit as a "tactical change" in military strategy that wouldn't deter efforts to defeat ISIS or hurt USA interests in the region.
U.S. national security adviser John Bolton suggested on Tuesday that protecting Washington's Kurdish allies would be a precondition of the United States withdrawal.
The Pentagon first gave word of the start of the withdrawal late Thursday. Ankara views U.S. Kurdish allies the YPG in Syria as one and the same with the PKK, a group that has waged a 34-year insurgency against Turkey.
A Kurdish politician told Reuters last week the Kurds had presented Moscow with a roadmap for a deal with Damascus.
The official provided no numbers, but said the equipment withdrawal is under way and that an unspecified number of additional USA troops have been brought into Syria to assist with the process, including by providing additional security. But that time frame has since been extended several times.
In a rare acknowledgment that French troops were also in Syria, he said they would leave when there is a political solution in the country.