WASHINGTON -- The top US military commander for Europe said here on Tuesday that the United States should not sell F-35 fighter jets to Turkey if Ankara buys Russian air defense system.

Testifying in a hearing of Senate Committee on Armed Services, General Curtis Scaparrotti, head of US European Command, suggested that the United States should cut the sale of F-35 fighters to Turkey if the latter adopts Russian-made S-400 air defense system.

Scaparrotti, who also serves as NATO Supreme Allied Commander Europe, said the S-400 system "presents a problem to all of our aircraft, but specifically the F-35."

"My best military advice would be that we don't then follow through with the F-35, flying it or working with an ally that is working with Russian systems, particularly air defense systems, with what I would say is probably one of most advanced technological capabilities," he added.

Also on Tuesday, US State Department said that Washington has made clear to Ankara that the potential acquisition of Russian air defense system would lead to a "reassessment" of Turkey's participation in the F-35 fighter program.

Turkey, a member of NATO, plans to buy 100 F-35 fighter jets. Turkish companies also play a key industrial role in the program as one of the producers of the center fuselage and the maker of the cockpit display, according to media reports.

The United States has repeatedly warned Turkey against purchasing Russian S-400 system. Last month at the Munich Security Conference, Vice President Mike Pence said that the United States "will not stand idly by while NATO allies purchase weapons from our adversaries."

Turkish President Recep Tayyip Erdogan said in response that his country would go ahead with the agreement with Russia to buy its defense system, and accused the United States of "coaxing Ankara into abandoning the S-400 deal."

Turkish Foreign Minister Mevlut Cavusoglu also said that S-400 was a done deal and the system would be delivered in the fall.