The United States continues to object “strenuously” to Turkey’s purchase of Russian missile defense systems and is “deeply concerned” with reports that Ankara is continuing its efforts to make the weapons operational, U.S. State Department spokeswoman Morgan Ortagus told Reuters on April 20.

“We continue to stress at the highest levels that the S-400 transaction is the subject of ongoing CAATSA sanctions deliberations and it remains a major obstacle in the bilateral relationship and at NATO. We are confident that President [Recep Tayyip] Erdoğan and his senior officials understand our position,” Ortagus said in an emailed statement, referring to the Countering America’s Adversaries Through Sanctions Act.

The United States says the S-400s, which Moscow delivered to Turkey last July, are incompatible with NATO defences and would jeopardise U.S. F35 stealth jets which Turkey planned to buy.

Ortagus’ remarks came after a senior Turkish official said that Turkey’s plans to switch on its S-400 Russian missile defense systems have been delayed by the coronavirus outbreak but it does not intend to reverse the decision.

“There is no going back on the decision to activate the S-400s (but) due to COVID-19 … the plan for them to be ready in April will be delayed,” the senior official said, speaking on condition of anonymity.

It could be several months before the Russian system is activated, the official said, adding some technical issues remained to be overcome.