US President Donald Trump last week warned Turkish counterpart Recep Tayyip Erdogan in a letter that he would soon have to impose sanctions on Turkey over its purchase of Russian-made S-400 missile defence systems if Ankara did not accept his proposed terms, Middle East Eye has learned.

According to MEE’s sources, Trump also said that Turkey could be re-admitted into a partner program for the US’s next-generation F-35 fighter jet if it agreed not to activate the S-400 systems and committed to not purchasing Russian weapons systems in the future.

Erdogan is scheduled to meet Trump on Wednesday in Washington with the issue of Turkey’s S-400 deal expected to be the main topic of conversation, even with the two NATO allies at odds over a range of issues including Ankara’s incursion into northern Syria to confront Kurdish forces formerly backed by the US.

The letter, according to two Washington sources who are familiar with the matter, aimed to lay the groundwork for the discussions between the two leaders this week.

Trump’s last correspondence with Erdogan, sent last month and threatening him with heavy sanctions over Turkey’s operation in northern Syria, caused uproar at the time because of its informal style which was perceived as undiplomatic and “childish“.

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