The United States has renewed its call on Turkey to renounce an advanced Russian air-defense system, rejecting a proposal by Ankara to resolve the dispute.
Defense Minister Hulusi Akar in an interview this week spoke of a compromise solution in which Turkey does not fully deploy the S-400s, which Russia originally built to target Western warplanes.
"Our policy vis-a-vis the S-400s has not changed," U.S. State Department spokesman Ned Price said when asked about the Turkish proposal on February 10.
"Russian S-400s are incompatible with NATO equipment, they threaten the security of NATO technology and they are inconsistent with Turkey's commitments as a NATO ally," Price told reporters.
"We have and continue to urge Turkey not to retain this system."
Akar mentioned the case of Turkey's historic rival, Greece, which bought Russia's older S-300 system after Turkish threats to attack Cyprus but did not make them fully operational.
U.S. officials have dismissed the comparison, saying the S-400 was a more advanced system.
Turkey went ahead with the deal with Moscow despite warnings from the United States, which under former President Donald Trump excluded Ankara from the F-35 fighter-jet program and imposed sanctions on Turkey's military procurement department.
Price also said that U.S. Secretary of State Antony Blinken was expected to speak with his Turkish counterpart, Foreign Minister Mevlut Cavusoglu, soon.
"I would expect the secretary and his Turkish counterpart will have an opportunity to chat, to connect in the coming days," he told reporters.
President Joe Biden vowed during the election campaign to toughen the U.S. stance on Turkish President Recep Tayyip Erdogan, whom he has described as an autocrat.