The US Senate passed a bill on Monday that could be used to block or slow the transfer of the F35 advanced warplane to Turkey, a NATO ally that has an increasingly strained relationship with Washington.
There have been bipartisan efforts in both the Senate and the House of Representatives, to potentially stop the transfer to Turkey.
The National Defense Authorization Act (NDAA) now needs to be reconciled with a bill from the House of Representatives and could be approved by the end of the summer.
The Senate version of the act is worth about $716bn.
Both houses have introduced their own version of amendments that target Turkey – one of the partner countries on the F35 programme.
The Senate version would prevent the transfer until the Pentagon devises a plan to remove Ankara from the programme.
The Republican party of US President Donald Trump controls both chambers.
In a reaction to the US Senate bill, Turkish Prime Minister Binali Yildirim on Tuesday criticised the US decision, calling it “an unfortunate development”.
“Turkey is not without alternatives. Such attempts are regrettable and go against the soul of strategic partnership,” Turkish daily Hurriyet quoted the prime minister as saying.
Ankara was seeking to buy about 100 of the stealth jets. However, various legislators have cited a number of concerns with Turkey, including its plans to buy advanced Russian air defence systems, warming ties to Moscow and the arrest of US citizens and consulate staff.
Turkish Foreign Minister Mevlut Cavusoglu on June 4 emphasised that if Washington decides not to sell F35s to Turkey, Ankara will look further to other countries or produce its own.
According to the F35 project agreement, the first two F35s must be handed over to Turkey in the US by June 21 for training and testing purposes.