Turkish President Recep Tayyip Erdogan has reiterated his country’s resolve to proceed with a purchase of advanced S-400 air defense missile system from Russia, a day after an informal deadline Washington set for Ankara to respond to a rival US offer passed.

Erdogan was quoted by Turkish broadcaster NTV on Saturday as saying that there was no turning back on the S-400 deal with Russia, and that Turkey was also interested in purchasing US Patriot missiles as long as Ankara’s interests were served.

“We have made the S-400 deal with Russia, so it is out of question to take a step back. The job is done. When it comes to the Patriots, we are open to buying them. However, this purchase needs to serve the interests of our country,” Erdogan told journalists on the way back from a trilateral summit in the Russian city of Sochi, where he met his Russian and Iranian counterparts to discuss developments in Syria.

“We are continuing our work based on the deal that the S-400s will be delivered in July,” the Turkish president added.