A senior U.S. official says the U.S. does not believe Russia's incursion into Turkey's airspace was an accident, and urgent talks are underway on what to do about the weekend incident.

The official says the event is the type of unprofessional military conduct that U.S. Defense Secretary Ash Carter spoke with the Russian defense minister about during their recent phone call.

Carter says the U.S. is conferring with Turkish leaders about the airspace violation and that the issue will come up later this week at the NATO meeting of defense ministers. Carter spoke during a press conference here with the Spanish defense minister.

The senior U.S. official was not authorized to discuss the talks publicly so spoke on condition of anonymity.