Congress is turning to the power of the purse in its efforts to force Turkey to choose between the US F-35 jet and a Russian missile-defense system.

The House foreign aid spending panel last week advanced annual spending legislation that would prohibit the Donald Trump administration from transferring the fifth-generation stealth aircraft to Turkey unless Secretary of State Mike Pompeo certifies that Ankara has scrapped plans to buy the S-400 from Russia. Lawmakers in both chambers have previously sought to block the F-35 sale as stand-alone bills, but including the language in the foreign aid spending package increases the likelihood that it will become US law.

Rep. Michael Turner, R-Ohio, joined Reps. Paul Cook, R-Calif., and John Garamendi, D-Calif., to introduce legislation blocking the sale earlier this month: the Protecting NATO Skies Act. Senate foreign aid panel members James Lankford, R-Okla., Jeanne Shaheen, D-N.H., and Chris Van Hollen, D-Md., have introduced the same bill in the upper chamber.

“Turkey is choosing to jeopardize its F-35 partner status for dealings with the Russian Federation,” Turner said in a statement introducing the bill. “It is imperative that we prevent our superior F-35 capabilities from falling into the wrong hands.”