The language used in a letter sent fromÂ United States to Ankara regarding Turkey's removal from the F-35 fighter jet programme does not suit "the spirit of alliance", Turkish Defence Minister Hulusi Akar has said.
US acting Secretary of Defence Patrick Shanahan's letter to his counterpart had outlined last week howÂ Turkey would be pulled out of the multi-countryÂ F-35 fighter jet programme unless Ankara changes course from its plans to purchase Russian S-400 missile defence system as of July 31.
Akar, cited by the defence ministry in a statement on Wednesday, also said Turkey is preparing a response to the letter and that it would be sent to the US in the coming days.Â
He added that he would hold a phone call with Shanahan on Thursday.
Shanahan, quoted by Turkey's state-run Anadolu news agency, also said on Tuesday that he will discuss the spat with Ankara with his Turkish counterpart over the phone.
Akar's statement comes a day after it was reported that Washington halted the training of Turkish F-35 pilots at an airbase in the US state of Arizona.
The move comes faster than expected, only days after Shanahan told Akar that Turkish pilots, who are already in the country, could remain until the end of July.
The USÂ saysÂ Turkey's missile defence acquisition from Russia poses a threat to Lockheed Martin's F-35 stealth fighters, whichÂ AnkaraÂ also wants to buy, adding thatÂ Turkey cannot have both.
President Recep Tayyip ErdoganÂ said many timesÂ it was "out of the question" for Turkey to back away from its deal with Moscow.
On Tuesday, Russia said it plans to deliver the system to Turkey in July.
The standoff threatens to bring US sanctions to Turkey, which would hurt the recession-hit economy, and raise questions over its role in the North Atlantic Treaty Organization.
Strains in American-Turkish ties already extend beyond the F-35 and S-400 to include conflicting strategy in Syria, sanctions onÂ Iran, and the detention of US consular staff inÂ Turkey.