The United States Senate approved the National Defence Authorisation Act (NDAA) for fiscal year 2019 on Monday putting a question mark over the proposed sale of F-35 fighter jets to Turkey.

The NDAA obliges the Secretary of Defence to present a report regarding the potential purchase of the S-400 air and missile defence system from Russia by the Turkish government. And until the report is presented, the Act put a stop to the US government from executing a foreign military sale.

Turkey is expected to receive its first lot of some 100 F-35 jets under a commercial contract starting next month.

Not later than 60 days after the date of the enactment of the Authorisation Act, "the Secretary of Defence, in consultation with the Secretary of State, shall submit to the appropriate congressional committees a report on the status of the United States relationship with the Republic of Turkey," the Act document said.

According to the Act, "the Secretary of Defense may not take any action to execute delivery of a foreign military sale for major defense equipment" to Tukey until the report is submitted.

The required report should include "an assessment of the potential purchase by the Government of Turkey of the S-400 air and missile defense system from the Russian Federation and the potential effects of such purchase on the United States-Turkey bilateral relationship, including an assessment of impacts on other United States weapon systems and platforms operated jointly with Turkey to include the F-35 Lightning II Joint Strike aircraft; the Patriot surface-to-air missile system; the CH-47 Chinook heavy lift helicopter; the AH-1 Attack helicopter; the H-60 Black Hawk utility helicopter; and the F-16 Fighting Falcon aircraft," the Senate said.

The Secretary of Defense is not allowed to take any action "to execute delivery of a foreign military sale for major defense equipment subject to congressional notification to the Republic of Turkey until the Secretary submits to the appropriate congressional committees the report," the Act said.

Separately, some 40 members of the US House of Representatives sent a letter to the US Defense Secretary James Mattis against the F-35 deal going through. "We must hold Turkey accountable for conduct that threatens US national security, undermines the interests of our partners and allies, and represents a broadside attack against fundamental democratic values," the lawmakers said. "For these reasons, we urge you to take whatever steps necessary to prevent the planned delivery of F-35 fighter jets to Turkey," the letter said.

The spat could also threaten Turkish Aerospace Industry's participation in the F-35 program where it is expected to manufacture the center fuselage of the aircraft.