President Recep Tayyip Erdogan said on Friday Turkey would turn elsewhere for fighter jets if the United States will not sell it the F-35 jets, adding that Ankara planned to start using the Russian S-400 missile defense system in April 2020. The United States said last week it was removing NATO ally Turkey from the F-35 program, as long threatened, after Ankara purchased and received delivery of the S-400 system that Washington sees as a threat. Washington has also threatened to impose sanctions on Turkey, though Ankara has dismissed the warnings. It has instead put its trust in sympathetic comments from US President Donald Trump, who has said that Turkey was treated "unfairly". However, Trump has not ruled out sanctions on Turkey. Erdogan, speaking publicly about the strained US ties for the first time in 11 days, said he hoped US officials would be "reasonable" on the question of sanctions, adding that Turkey may also reconsider its purchase of advanced Boeing aircraft from the United States. "Are you not giving us the F-35s? Okay, then excuse us but we will once again have to take measures on that matter as well and we will turn elsewhere," Erdogan told members of his ruling AK Party. "Even if were not getting F-35s, we are buying 100 advanced Boeing aircraft, the agreement is signed... At the moment, one of the Boeing planes has arrived and we are making the payments, we are good customers," he said. "But, if things continue like this, we will have to reconsider this." "In the coming spring, God willing in April 2020, we will be able to start using this system," he added. "I hope the US will act with good sense regarding the S-400," Erdogan stated. Russias Rostec state conglomerate said Russia would be ready to supply its SU-35 jets to Turkey if Ankara requested them. But, Turkish officials said on Thursday there were no talks with Moscow on alternatives to the F-35 jets for now. Ties between Ankara and Washington have been strained over a host of issues. Turkey has also been infuriated with US support for the Kurdish People’s Protection Units (YPG) in Syria, a main US ally in the region that Ankara sees as a terrorist organization. Ankara has warned that it would launch a military operation in northern Syria to wipe out the YPG if it could not agree with Washington on the planned safe zone in the region, saying it had run "out of patience." However, Erdogan said on Friday that Turkey is determined to destroy the "terror corridor" east of the Euphrates river in Syria no matter how talks on the safe zone conclude, as Ankara ramped up its threats of an offensive.