Defense Minister Hulusi Akar said on Friday US officials have told Turkey it would be impossible for Congress to approve the sale of F-35 jets if Ankara buys the Russian S-400 air defense system, but that Turkey is working to overcome those problems.
Turkey says it has already paid Moscow some of the bill, and analysts say President Recep Tayyip Erdogan, who is campaigning for March 31 local elections, would find it hard to back away from the Russian deal now.
The US had agreed to sell 100 of its latest, fifth-generation F-35 fighters to Turkey, and has so far delivered two of the aircraft. But Congress last year ordered a delay in future deliveries.
Erdogan said that his country will go ahead with the purchase of S-400 system, despite a US warning that such a move would force it to cancel a sale of the F-35 jets to Ankara.
In an interview with Kanal 24 television late Wednesday, he said: "The S-400 is a done deal, there can be no turning back. We have reached an agreement with the Russians."
"We will move toward a joint production. Perhaps after the S-400, we will go for the S-500."
Erdogan added that first delivery of the S-400 would be made in July.
This week, the top US military commander for Europe, Gen. Curtis Scaparrotti, told the US Congress that NATO member Turkey should reconsider its plan to buy the S-400 from Russia or forfeit other future American military aircraft and systems.
He said Turkey's use of the Russian surface-to-air missile defense system would be a threat to the F-35.
It was the latest in a series of warnings the US has made to Turkey over its plans to buy the S-400. The US and other NATO allies have repeatedly complained about the purchase, saying it is not compatible with other allied systems and would represent a security threat.
The issue has aggravated already souring relations with Ankara, including tensions over the war in Syria.
In December, the State Department approved the sale of a $3.5 billion US Patriot missile defense system to Turkey.
Erdogan said Turkey could still purchase the Patriot system "if the conditions are suitable, the prices are suitable (and) if we can conduct a joint production."
The last diplomatic crisis between the two countries contributed to driving the lira to a record low in August.
This week, despite the Central Bank maintaining interest rates well above inflation, Turkey’s currency has fallen 1.5 percent - largely due to renewed concerns over relations with Washington, traders say.