By Staff, Agencies

Russia plans to deliver its S-400 missile defense systems to Turkey in July, Kremlin aide Yuri Ushakov told reporters on Tuesday.

NATO member Turkey's S-400 deal with Moscow has angered the United States, which has threatened to remove Ankara from its F-35 fighter jet program unless Turkey pulls out of the deal.

"The agreements reached between Russia and Turkey are being fulfilled on time in the given context. There are no bilateral problems," Kremlin aide Yury Ushakov told reporters on Tuesday. Asked if the missiles would be delivered in July, he said: "Yes, that's what we plan somehow." 

The comments came days after the head of Russian state conglomerate Rostec, Sergei Chemezov, said Moscow would start delivering S-400 missile systems to Turkey in two months, contradicting several Turkish officials who said the delivery could take place as soon as June. 

On Monday, Turkey complained that the United States had not yet taken up its suggestion of creating a joint working group to try to defuse tensions over Ankara's purchase of the S-400s. 

In the meantime, training by Turkish pilots on F-35 fighter jets came to a halt at a US air base in Arizona, US officials said on Monday. If Turkey were removed from the F-35 program, it would be one of the most significant ruptures in recent history in the relationship with the United States, experts said.