ANKARA, Aug. 31 (Xinhua) -- Turkey is determined to purchase Russian-made S-400 missile defense systems soon despite objection pressure from the United States, Turkish President Recep Tayyip Erdogan said on Friday.

"Turkey needs the S-400 missiles and the deal is done. We will procure them as soon as possible," he said at a graduation ceremony for military officers in western Balikesir province, reported by the state-run Anadolu Agency.

The United States has expressed concern that Turkey's planned deployment of the S-400s could risk the security of some U.S.-made weapons in NATO and other technology used by Turkey, including the F-35 jet.

Erdogan said Turkey also needs F-35 fighter jets and will continue to pay its installments to procure them from the United States, but would procure jets elsewhere if the U.S. halts the delivery of the F-35 planes.

"The fight against terrorism seems to be the right of every nation but Turkey," said the Turkish leader. "It is not possible for Turkey to accept such impositions," criticizing the U.S. efforts aiming at preventing Turkey to acquire the modern jet fighters.

The United States has prohibited recently the delivery of F-35 fighter planes to Turkey until the Pentagon submits an impact assessment on U.S.-Turkish relations as a whole.

The bilateral relations are deteriorating in recent months over the detention of a U.S. pastor in Turkey, who is charged with terrorism and espionage.