ANKARA, May 28 (Xinhua) -- Turkish Defense Minister Hulusi Akar said the delivery of Russian S-400 systems to Turkey "might be delayed until after June," local media reported on Tuesday.

"They may not catch June, but will arrive in following months. The process has started," Akar said late Monday in an interview with private broadcaster HaberTurk.

"There are some details about the agreements we have made regarding the procurement of the S-400, within the framework of the contracts. Related institutions and organizations continue to negotiate about them," the minister said when asked about the arrival time of the air defense systems.

Turkish defense ministry is working on the possible locations where the S-400 batteries will be deployed, he said.

In April, Akar said Turkey was expected to receive Russian S-400 air defense batteries by June. The missile batteries are most likely to be used for the defense of capital Ankara and Istanbul.

The United States threatens to suspend the delivery of the F-35 fighter jets and slap sanctions if Turkey insists on the purchase of the S-400s.