Top U.S. officials have spoken "with all of our counterparts, urged them to stop this incursion," U.S. Defense Secretary Mark Esper told reporters in a briefing citing the destabilizing effects it is having throughout the region.
"The dramatic harm I feel is being done to our bilateral relationship," Esper added.
He also said the U.S. was not abandoning its Kurdish partners.
"We have not abandoned the Kurds, let me be clear about that," U.S. Defense Secretary Mark Esper told reporters at the Pentagon.
"Nobody green-lighted this operation by Turkey, just the opposite. We pushed back very hard at all levels for the Turks not to commence this operation," Esper said.
Turkey stepped up its air and artillery strikes on Kurdish militia in northeast Syria on Friday, escalating an offensive that has drawn warnings of humanitarian catastrophe and turned Republican lawmakers against U.S. President Donald Trump.
The Kurdish YPG is the main fighting element of the Syrian Democratic Forces (SDF) which have acted as the principal allies of the United States in a campaign that recaptured territory held by the Islamic State group.
The SDF now holds most of the territory that once made up Islamic State's "caliphate" in Syria, and has been keeping thousands of Islamic State fighters in jail and tens of thousands of their family members in camps.
Esper said he had spoken with his Turkish counterpart about the harm the Turkish incursion was having on relations between the United States and Turkey, which are NATO allies.