FILE PHOTO: People walk past Russian S-400 missile air defence systems before the military parade to commemorate the 75th anniversary of the battle of Stalingrad in World War Two, in the city of Volgograd, Russia February 2, 2018. REUTERS/Tatyana Maleyeva/File Photo

ISTANBUL (Reuters) - Turkey is to accept delivery of a second battery of Russian S-400 missile defenses beginning on Tuesday, Defence Minister Hulusi Akar said on Monday according to state-owned Anadolu news agency.

The initial parts of the system, which Washington says are not compatible with NATO defenses, were delivered to Ankara in July despite warnings about possible U.S. sanctions over the purchase.