Russia insisted Turkey was not allowed to re-export S-400 missiles on its own, after the US senator proposed to buy the system from Ankara.

"In order to export defense products, our weapons buyers must provide the end-user declaration to the Russian side. That's why customers cannot transfer or re-export those weapons to the third country."

The announcement came after US Sen. Whip John Thune last week submitted to Congress a proposal to amend the Defense Authorization Act (NDAA) 2021, which proposed using the U.S. Army budget to buy a system.

Senator Thune made the proposal amidst the Washington-Ankara tensions remain high because Turkey bought Russia's S-400 air defense missile system instead of the US Patriot.

However, Turkey did not accept the requirements and decided to operate the S-400 system.

Turkey then threatened to buy Russian fighters to replace the F-35 and warned of the closure of two US strategic bases in its territory.