Turkey's defense minister on Wednesday objected to a letter sent by the USA, saying it "is not in line with the spirit of alliance".
Turkey on Wednesday criticised a letter from Washington on Ankara's eventual removal from the F-35 fighter jet programme, saying the language used did not suit the spirit of alliance between the two North Atlantic Treaty Organisation allies.
Erdogan's statement follows an earlier remark made by acting US Defence Secretary Patrick Shanahan that Ankara was notified about a potential ban on obtaining the F-35 fighter jets it had already purchased if it proceeded with the S-400 deal. He added that he would be speaking by phone with Shanahan on Thursday.
Shanahan, quoted by Turkey's state-run Anadolu news agency, confirmed on Tuesday that he meant to discuss the spat with Ankara with his Turkish counterpart.
Turkey and the United States have sparred publicly for months over Ankara's order for the S-400s, which are not compatible with the NATO's systems. "We haven't suspended any of the maintenance activity", the letter said.
Washington maintains the move will jeopardize Turkey's role in the U.S. F-35 fighter jet program and could trigger congressional sanctions.
But the Pentagon said June 11 that the U.S. Air Force has halted ongoing training of Turkish pilots on the F-35 before the end date for "safety" concerns.
Turkey has already bought S-400 defense systems from Russian Federation and hopes they will be delivered in July, Turkish President Tayyip Erdogan said on Wednesday, an announcement likely to ratchet up tensions with Washington on the issue.
US officials argued it would be incompatible with North Atlantic Treaty Organisation systems and expose the F-35 to possible Russian subterfuge, but Turkey has emphasized that the S-400 would not be integrated into North Atlantic Treaty Organisation operability and would not pose a threat to the alliance.