Turkey will honor its air defense deal with Russia, Ankara said on Friday after four US senators introduced a bill to ban the planned delivery of F-35 fighter jets if Turkey ignored US opposition and accepted the S-400 system.

“We have agreed with Russia in the end and signed an agreement. This agreement is valid [and] we are discussing when the delivery will be,” Turkish Foreign Minister Mevlut Cavusoglu said following a meeting with his Russian counterpart.

“This agreement is a done deal.”

The US senators on Thursday introduced a bipartisan bill to prohibit the transfer of F-35 aircraft from the United States to Turkey until the US government certifies that Ankara will not take delivery of the Russian S-400 system, a statement on the move said.

Turkey has been receiving contradictory statements from the United States, Cavusoglu said, adding Ankara has met all its obligations related to the F-35s, which are made by Lockheed Martin Corp.

Turkey is a production partner in the trillion-dollar F-35 fighter jet program but the United States, a NATO ally, has opposed its purchase of Russian systems which could compromise the security of the aircraft.

Turkey had no intention of selling the S-400s to another country, Cavusoglu said. [Reuters]