The suspension of F-35 Joint Strike Fighter sales to Turkey has become more likely after both the House and Senate opposed the deal in their versions of the 2019 National Defense Authorization Act.

The Defense Department has 90 days from the bill's final passage to submit a report to lawmakers explaining the strategic value of selling the jet to Turkey, a member of NATO. Until that time, deliveries of the fifth-generation fighter to Turkey will be on hold, House aides told reporters Monday, The Hill reported.

The latest move comes weeks after Defense Secretary Jim Mattis encouraged lawmakers to reconsider. "At this time, I oppose removal of Turkey from the F-35 program," he said in a letter earlier this month.

Turkey, a coalition member in the fight against the Islamic State, plans to buy more than 100 F-35As, the conventional takeoff and landing model of the stealth fighter. The first delivery is expected this year.

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But Mattis and members of Congress have not been happy that Turkey has also made a deal to acquire Russia's S-400 surface-to-air missile system, known by Moscow as the "F-35 killer."

"Ultimately, we are concerned that by purchasing these systems from the Russians, it will be supportive of some of the least good behavior that we have seen from them in various places, including in Europe but also elsewhere," said Tina Kaidanow, acting assistant secretary for the Bureau of Political Military Affairs at the State Department.

The State Department has been quietly trying to push Turkey to reconsider the S-400 buy in favor of the U.S.-made Patriot missile system.

"That's true of a number of our partners. It's not just ... the Turks, as I said," Kaidanow told reporters last week during the Farnborough Airshow.

Lawmakers in April voiced concern over the missile purchase and attempted to block the sale of F-35s to Turkey over the "increased risk" its recent actions pose to U.S. interests.

Sens. Jeanne Shaheen, D-N.H.; James Lankford, R-Okla.; and Thom Tillis, R-N.C., introduced a measure April 26 that would pause the transfer of the F-35A. It would also block Turkey from having a role in depot maintenance for the aircraft.

In 2017, Rep. David Cicilline, D-R.I., a member of the House Foreign Affairs Committee, proposed an amendment to the 2018 National Defense Authorization Act that would ban the sale of F-35s to Turkey after members of Turkish President Recep Erdogan's security detail were seen beating protesters outside the Turkish embassy in Washington, D.C.

The House is expected to vote on the conference version of the NDAA this week; the Senate should vote on the bill in August.

-- Oriana Pawlyk can be reached at oriana.pawlyk@military.com. Follow her on Twitter at @Oriana0214.