The White House confirmed on Monday that Trump and Erdogan had discussed Turkey’s planned purchase of the S-400 missile defense system ANKARA: US President Donald Trump and Turkish President Tayyip Erdogan in a phone call on Monday discussed a Turkish proposal to create a joint working group on its planned purchase of a Russian S-400 missile defense system, the Turkish Presidency said. “Our Honourable President brought up the proposal to establish a working group regarding the procurement of the S-400 defense system from the Russian Federation,” it said. The two countries have argued for months over Turkey’s order for the missile defense system, which the United States says is incompatible with NATO’s defense network and could compromise its F-35 fighter jets. Ankara has said a working group could assess the impact of the S-400 on the fighter jets, but on Friday said that it has not heard back from the Americans. The White House confirmed on Monday that Trump and Erdogan had discussed Turkey’s planned purchase of the S-400 missile defense system. US Secretary of State Mike Pompeo and several US senators have warned Turkey it will face penalties for buying S-400s under a law that calls for sanctions against countries procuring military equipment from Russia. Turkey has said that as a NATO member, it poses no threat to the United States and the sanctions should not apply. Trump and Erdogan also discussed trade and the ongoing crisis in Syria, the White House said.