Turkish President Recep Tayyip Erdogan said Wednesday that Ankara may bring forward from July the delivery of the Russian S-400 missile defense system, reported the Sabah newspaper. “We answer that ‘this deal is done, everything is settled’. The delivery of the S-400 missile defense system was to be in July. Maybe it can be brought forward,” Erdogan said. The purchase has put Ankara at odds NATO ally the United States. The S-400s are not compatible with NATO systems and Washington says Turkey’s purchase of them would compromise the security of F-35 fighter jets, which are built by Lockheed Martin Corp. Turkey is involved in F-35 production. Erdogan told reporters on his plane while returning from a trip to Russia this week that he and his foreign minister were constantly being asked about the S-400 purchase and being pressured to abandon it. On Tuesday, leaders of the US Senate Foreign Relations and Armed Services Committees warned Turkey that it risked tough sanctions if it pursued plans to buy the S-400s, and they threatened further legislative action. “By the end of the year, Turkey will have either F-35 advanced fighter aircraft on its soil or a Russian S-400 surface-to-air missile defense system. It will not have both,” Republican Senators Jim Risch and Jim Inhofe and Democratic Senators Bob Menendez and Jack Reed said in a New York Times opinion column. Meanwhile, Foreign Minister Mevlut Cavusoglu said Turkey may expand its purchase of the Russian system if it cannot buy US Patriots missile defense systems. He also said Turkey had not received a positive response from Washington over its proposal to form a joint working group to look into Ankara’s deal with Moscow.