Turkish President Tayyip Erdogan dismissed on Wednesday Western concern over Turkey’s deal to procure an S-400 air defense system from Russia and said the NATO member will continue to take its own security measures.

“They went crazy because we made the S-400 agreement. What were we supposed to do, wait for you? We are taking and will take all our measures on the security front,” Erdogan said.

Western governments have expressed concern over the deal as it cannot be integrated into the NATO system. Turkey has said that NATO allies had not presented a “financially effective” offer on alternative missile defense systems.

Erdogan said in July that the deal had been signed, although the deal appears to have been drawn out since then, due to issues over financing. Turkish media quoted Erdogan this week as saying he and Russian President Vladimir Putin were determined that the agreement should proceed.

The decision to procure the Russian system comes as Turkey finds itself frequently at odds with NATO allies, particularly the United States and Germany. Ankara has been angered by U.S. support for the YPG Kurdish fighters in the battle against ISIS in Syria.

The US Pentagon said it had expressed concerns to Turkey about the deal.

“We have relayed our concerns to Turkish officials regarding the potential purchase of the S-400. A NATO interoperable missile defense system remains the best option to defend Turkey from the full range of threats in its region,” spokesman Johnny Michael said in a statement.

source: Alarabiya