Turkey’s decision to buy the advanced Russian-made air defence system has led to a significant souring of relations with Washington, which has threatened to slap Ankara with sanctions and to deprive the country of the F-35 fighters it had already bought and paid for. The first batch of Turkey-bound S-400s will be loaded onto planes at a Russian military base this coming Sunday and sent to Turkey sometime next week, Haberturk TV has reported, citing unnamed sources. According to the TV channel’s information, the delivery will be made using two cargo planes, with a team of nine Russian engineers responsible for installing the system in Turkey to arrive in the country by Monday. The delivery will bring one complete S-400 missile system to Turkey, Haberturk specified. On Thursday, a spokesman for the Turkish president said Ankara would receive its Russian-made air defence systems “very soon, in the coming days,” and promised that they “will be actively used.” The spokesman added that authorities are still examining options about where the S-400s will be placed, with discussions previously held about deploying them in Qatar or Azerbaijan to avoid exacerbating Turkish-US tensions over the purchase. Authorities had originally discussed placing the air defence systems around the Turkish capital. During their meeting in Osaka, Japan at the G20 summit last week, President Trump told Turkish President Recep Tayyip Erdogan that Washington treated Ankara ‘unfairly’ over its missile deal with Russia, blaming his predecessor Barack Obama for refusing to supply Turkey with its Patriot missile systems ahead of time. “You have to treat people fairly…and I don’t think he was treated fairly,” Trump said. In spite of Trump’s comments, the US has continued to threaten Turkey with sanctions under the Countering America’s Adversaries Through Sanctions Act (CAATSA), and has warned that it may drop Ankara from the F-35 fighter programme and scrap plans to deliver the planes to the country. Turkey, which has invested over a billion dollars into the programme and produces several components for the aircraft, has yet to take possession of a single F-35, with four F-35s destined for Turkey remaining at a US airbase. Last month, Turkish pilots training aboard the aircraft were grounded. Earlier in the week, commenting on the F-35 holdup, Erdogan accused the US of engaging in “robbery,” recalling that Washington and Ankara had previously signed an agreement on the sale of 116 F-35s to Turkey. Russia and Turkey penned a $2.5 billion agreement on the sale of four battalion sets of S-400s to Turkey in late 2018. A year later, the US cleared a $3.5 billion Patriot missile deal for the country, but Ankara has yet to accept it, saying its terms aren’t as good as those provided by Russia for the S-400s, which include a loan agreement. US and NATO officials have repeatedly alleged that the S-400 is ‘incompatible’ with alliance air defence standards, and claimed the system’s presence in Turkey might allow Russia to collect important information about the F-35 and other NATO systems. In May, a senior Pentagon official said the deployment of S-400s in Turkey would be “devastating,” both for the F-35 programme and in terms of Turkish interoperability with NATO.