WASHINGTON — The top uniformed officer in NATO and the head of American forces in Europe said Tuesday that if Turkey goes through with its decision to buy a Russian air defense system, he would recommend the Pentagon refuse to give Ankara its planned purchase of the F-35 joint strike fighter.

Testifying in front of the Senate Armed Services Committee, Gen. Curtis Scaparrotti said it would be his “best military advice" that sales to Turkey of the F-35 be cut, should that nation buy the S-400 air defense system.

“If they accept the S-400 to establish it in Turkey, there is first the issue that it’s not interoperable with NATO systems, nor is it interoperable inside of our integrated missile defense system. The second has to do with the F-35. It presents a problem to all of our aircraft, but specifically the F-35, I believe,” Scaparrotti said.

“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 one of our most advanced technological capabilities,” he added.

The comments came in an exchange with Sen. Jeanne Shaheen, D-N.H., who has sponsored legislative language to to explore Turkey’s removal from the F-35 program.

Concerns about Turkey’s decision to procure the S-400 are nothing new. Officials in the U.S. and Europe believe Russia could gain a dangerous amount of information on the fifth-generation fighter should the systems be linked.

But Scaparrotti’s statement is particularly notable, as he also serves as supreme allied commander of NATO. His comments come weeks after the Munich Security Conference, where U.S. Vice President Mike Pence warned Turkey that “we will not stand idly by while NATO allies purchase weapons from our adversaries. We cannot ensure the defense of the West if our allies grow dependent on the East."

Turkey plans to buy 100 joint strike fighters over the course of the program, and its first F-35 pilots have already begun training alongside U.S. pilots at Luke Air Force Base, Arizona. Turkish companies play a key industrial role in the program as one of the producers of the center fuselage and the maker of the cockpit display.

As a result of the planned S-400 procurement, the Pentagon launched a large study into whether it would be possible to remove Turkey from the F-35 industrial base.

Asked about the industrial base, the general said: “For them I would underscore this is a huge decision for Turkey. I have talked to them, as all of our leadership has.” He added that there is a team on the ground today talking with the Turks about the issue.

“I would hope they would reconsider this decision on the S-400, one system, but potentially forfeit many of the other systems and one of the most important systems we provide them," he said.

One such system besides the F-35 that could be impacted should Russia buy the S-400 is the Patriot missile defense system, which Turkey was recently cleared to buy.

Valerie Insinna in Washington contributed to this report.