Turkey set course for a clash with its NATO allies on Friday morning when the first shipment of a Russian S-400 missile defense system arrived, the Turkish Defense Ministry confirmed.

The delivery also pushed the country closer to possible U.S. sanctions and a new diplomatic standoff.

Washington has previously told its NATO ally that Ankara’s adoption of Russian S-400 missile technology alongside high-tech U.S. F-35 fighters was incompatible and would endanger Western defence.

“We have . . . been clear that acquisition of the [Russian] S-400 is not compatible with the F-35,” Lt. Col. Mike Andrews, a Department of Defense (DOD) spokesman declared in a statement issued in April. “We very much regret the current situation . . . but the DOD is taking prudent steps to protect the shared investments made in our critical technology.”

The S-400 is the latest generation surface-to-air defense system developed by Russia as a rival for America’s own Patriot weaponry, and is considered by NATO countries to pose a threat to their combined air operations.

A Defense Ministry statement said “the first group of equipment” of the S-400 air defense systems has reached an air base near the capital, Ankara.

The United States suspended the delivery of F-35 warplane-related equipment to Turkey in April until Ankara ditched the Russian deal, which now appears unlikely.

The U.S. has repeatedly said the Russian S-400 system is a threat to the integrity of NATO defense and is a threat to the F-35.

AP contributed to this report