Three F-35A Lightning-IIs assigned to the 4th Expeditionary Fighter Squadron taxi after landing at Al Dhafra Air Base, United Arab Emirates, April 15, 2019. The F-35A Lightning II is deployed to the U.S. Air Forces Central Command area of responsibility for the first time in U.S. Air Force history.

The United States earlier threatened to remove Turkey from it's F-35 program after Ankara refused to scrap a deal with Russia to buy Moscow's cutting-edge S-400 missile systems, which Washington claimed could compromise US-made aircraft.

Ankara will consider purchasing Russian fighter jets as well if Washington refuses to deliver the F-35 aircraft to Turkey according to Turkish officials, cited by Bloomberg.

Turkish President Recep Tayyip Erdogan said Saturday that he discussed with US President Donald Trump the latter's possible visit to Turkey, as well as Ankara's intention to purchase Moscow's S-400 air defence systems alongside the purchase of US F-35 stealth fighter jets.

"We talked about our relations with the United States, we talked about the S-400s, we talked about F-35s and about what we could further achieve together. And we talked about a possible visit of Trump to Turkey", Erdogan said, on the sidelines of the G20 summit in Japan.

Erdogan also stressed that he believed the dispute with the US over the S-400s would be overcome "without a problem" and added that Trump supports Turkey in the row, according to Reuters.

Meanwhile, Ankara will take delivery of the Russian S-400 air defence system within days, Bloomberg reported on Monday, citing Turkish media. In particular, the first batch of S-400s will be delivered in 7-10 days, according to Bloomberg, citing the Haberturk newspaper.

Washington has repeatedly objected to the purchase of Russian-made defence systems by its NATO ally, claiming that the S-400 is incompatible with NATO security standards. In June, the Pentagon warned Ankara that the delivery of 100 purchased F-35 fighter jets could be halted and training for Turkish pilots on the new jets would be cancelled if Turkey purchases Russian missile systems.

In December 2017, Moscow and Ankara signed a loan agreement for the delivery of the S-400 air defence systems to Turkey. In spite of US threats to impose sanctions against Ankara, Turkish officials went forward, noting that the purchase of military equipment is a sovereign right while ruling out the possibility of abandoning plans to acquire the S-400 systems.