Washington said in July that Turkey would be excluded from the F-35 programme after Ankara bought the Russian S-400 air defence systems.

The US fears Russia could glean technical secrets about the new fighter jet if it is operated alongside the S-400.

"There is not yet any official letter, statement or a notification about Turkey's exclusion from the F-35 programme despite partial steps including the ending of our pilots' training," Turkish presidential spokesman Ibrahim Kalin told reporters in Ankara after a weekly cabinet meeting.

He said the issue would be discussed during a possible meeting between Turkish President Recep Tayyip Erdogan and his US counterpart Donald Trump on the sidelines of the annual UN General Assembly in New York later this month.

"Turkey is not a customer to F-35 but a partner. To scrap Turkey from this programme would have a very serious economic cost," Kalin said.

The US argument that the F-35 cannot coexist with the S-400 was not convincing, he said, adding that Ankara was ready to take steps to eliminate security concerns in bilateral talks with American officials and with NATO.

"We have not given up on the F-35 programme. It is not that easy to remove Turkey from that programme," Kalin said.

"That would have serious consequences. We believe the crisis will be overcome sooner or later."

Ankara had ordered more than 100 F-35 jets and its defence industry has invested significant sums in the plane's development.