Acting U.S. Defense Secretary Patrick Shanahan reiterated his country's opposition to Turkey's purchase of the Russian S-400 missile defense system, saying that Pentagon will halt manufacturing support for the F-35.
Shanahan told journalists the government remained steadfast in its opposition to Turkey's adoption of the S-400 anti-aircraft technology.
"If Turkey decides that the S-400 is a decision they want to go forward with, then we have to move work out of Turkey," he said.
Shanahan noted that he had met with delegations from U.S. aerospace manufacturers Lockheed Martin and United Technologies to discuss options if Turkey refuses to forego the S-400.
Washington has warned for months that Turkey's adoption of Russian missile technology alongside U.S. fighter jets would pose a threat to the F-35 and endanger Western defense.
As a member of NATO, Turkey is taking part in the production of the fighter jet for use by members of the treaty, and has plans to buy 100 of the jets itself.
Ankara's ties with Washington have been strained over Turkey's decision to buy the Russian-made defense system, and U.S. officials threatened Turkey's removal from the F-35 program, halting the delivery of jets to the country and excluding Turkish manufacturers from joint production. However, Turkey received two more jets two weeks ago after the delivery of the first batch in June 2018, and four Turkish pilots currently continue their training at the Arizona base.
Like other NATO allies of Washington, Turkey is both a prospective buyer and a partner in production of the F-35, which has been beset by cost overruns and delays, and entered service in the United States in 2015.
Ankara has proposed a working group with the United States to assess the impact of the S-400s, but says it has not received a response from U.S. officials.
The Ankara-Moscow S-400 deal was inked in December 2017, when the parties signed a $2.5 billion agreement for two batteries of the systems – Russia's most advanced long-range anti-aircraft missile system in use since 2007.