By Selcan Hacaoglu, Bloomberg

Turkey said it can’t accept the U.S. proposal for the sale of Patriot air defense systems unless it’s revised, and that it expects Russia to deliver S-400 missiles as early as July, developments that could threaten a brittle detente between Ankara and Washington.

Ismail Demir, head of the main state body dealing with arms procurement and production, didn’t clarify on Wednesday what was objectionable. But President Recep Tayyip Erdogan said last week that joint production, financing and delivery time will decide whether Turkey buys the American system. And he insists that Turkey will take the Russian missile system either way, saying traditional allies in the West failed to meet his country’s defensive needs.

Ankara’s dissatisfaction with the U.S. proposal could renew years of strain on multiple fronts that culminated with since-lifted U.S. sanctions on Turkey. After balking for years at selling Turkey its Patriot missile defense system, the U.S. State Department notified Congress in December that it had proposed doing just that, a gambit designed to get Ankara to halt the S-400 deal, which could compromise NATO technology.

“It is not possible for us to accept the content and details of the proposal as it is at the moment,” Demir told NTV television in an interview. “The conditions must be discussed, there are a series of issues that must be clarified and a compromise must be reached.”

Demir said the delivery of the first S-400 missile defense system was expected to start in July and “activated by October.” The shipment of the second system will be postponed “for a while,” he added. Russia has promised Turkey joint production and technology transfer as part of the agreement, a key Turkish demand.

Turkish-U.S. ties remain rocky over a series of disputes including Washington’s support for a Syrian Kurdish force that Ankara regards as a mortal enemy; Turkey’s demand that the U.S. extradite a preacher it accuses of instigating the failed coup attempt in 2016; and the conviction of a Turkish banker on Iran sanctions violations charges.

Turkey is also growing impatient over the delayed withdrawal of U.S. troops from Syria. In the meantime it’s been pressuring Washington to force its allied Kurdish forces out of the town of Manbij. Turkey has amassed troops near Manbij and along the border with northeast Syria, threatening to attack U.S.-backed Kurdish forces at any time.

Ankara regards the Kurdish fighters’ separatist agenda as a threat to its own territorial integrity, regarding them as an offshoot of the Kurdish separatist PKK group it’s battled for decades at home.