Turkey is set to begin testing the newly acquired Russian S-400 missile defences in spite of pressure from the US to stop the programme.

The US claimed that the S-400 system is incompatible with Nato defences and could pose a threat to F-35 stealth fighter jets from Lockheed Martin.

In an announcement, the provincial governor’s office stated that the Turkish Air Force F-16s and other aircraft will conduct flights over Ankara on Monday and Tuesday to test the S-400 air defence system.

A Turkish Defence official was reported to have said that military aircraft will be used in Ankara during the testing of the S-400 system’s radar-detection equipment for two days. Milliyet publication reported that the military plans to test S-400s that are deployed at an airbase on the outskirts of Ankara.

Turkey took possession of two S-400 batteries this year even though the US warned that they pose a threat to Nato security. Turkey’s action prompted the US to suspend Turkish participation in the multinational F-35 fighter jet programme, which the European country was involved in as a buyer and producer.

A section of the media reported that the flights were intended to test the S-400 system. Ankara began receiving the S-400s last July, but they are not yet operational.

During a meeting earlier this month, US President Donald Trump reportedly told Turkish President Tayyip Erdogan that the US is willing to sell its Patriot systems if Turkey cancels the S-400 system.

The S-400 system is reportedly designed to bring down aircraft such as those used by the US and allies at greater ranges and altitudes compared to older missiles.

US officials voiced concern that sensitive technology in the F-35 fighter plane designed to evade systems such as S-400 could be compromised and used to improve Russian technology in case Turkey possesses both.

The US has also warned Turkey of possible sanctions over the S-400 deal.

Meanwhile, reports of the planned tests and the fallout with the US had an impact on the Turkish lira, which declined to 5.7380 against the US dollar from a close of 5.7140 on Friday.