Turkey’s President Erdogan says he hopes a Russian missile system that Washington sees as a threat to US jets will be delivered in July.
The US had said Turkey could not have both the S-400 anti-aircraft defence system and US F-35 fighter jets.
But Mr Erdogan said Turkey would hold to account anyone who excluded Turkey from the F-35 programme.
Nato member Turkey has signed up to buying 100 F-35s and has invested heavily in the F-35 programme.
Turkish companies produce 937 of the plane’s parts.
Mr Erdogan said he hoped to resolve the situation with the US through phone diplomacy ahead of a meeting with President Trump at the end of June, Reuters reported.
Turkey has been pursuing an increasingly independent defence policy and has been establishing closer links with Russia after a recent souring of its ties with the US and Europe.
What has the US been telling Turkey?
US acting Secretary of Defence Patrick Shanahan last week wrote to his Turkish counterpart that the US was “disappointed” to hear that Turkish personnel have been sent to Russia to train on the S-400.
Another senior US official, Under Secretary of Defence Ellen Lord, told reporters that the US did not want Russian technicians to be able to access the F-35’s vulnerabilities.
“We do not want to have the F-35 in close…