s-400

“Ankara appears to be on a crash course – not only with its neighbors but also with the entirety of its NATO allies,” expert says.

Sources said the announcement of the sanctions in their current form was imminent, while a Turkish official called them "unproductive."

Russia delivered the ground-to-air S-400s last year and Turkey tested them as recently as October.

State Department spokeswoman Morgan Ortagus said the US has expressed to the Turkish government that the acquisition of Russian military systems such as the S-400 is unacceptable.

The tests last year were already known, so Russia’s agenda of discussing them again may be linked to a wider one.

Making the S-400s operational exposes Turkey to US sanctions under legislation designed to punish countries which buy defense equipment from Russia.

U.S. lawmakers will vote - and likely pass - a defense bill later on Wednesday that calls for sanctions against Turkey over Ankara's decision to procure the S-400 defenses.

"The time for patience has long expired," Republican Lindsey Graham and Democrat Chris Van Hollen said.

Moscow hopes to seal a deal to supply Turkey with more S-400 missile systems in the first half of next year.

Qatar’s security and defense cooperation are the backbone of the Doha-Ankara alliance, Erdogan said. “We have deep relations in the Gulf.”