The US State Department sent a letter to Congress on July 22 stating that Turkey has not yet met the requirements necessary for the sale of F-35 fighters, according to Fox News, which has obtained the document.

The letter states that US law prohibits the transfer of F-35s to Turkey as long as the latter has Russian S-400 air defense systems and related equipment, as well as until it has committed not to purchase them in the future and has met other certification requirements set by Congress.

Turkey has not yet met these conditions, according to the US State Department letter sent to Capitol Hill.