Doha is negotiating the purchase of Russian S-400 missile air defense systems, TASS quoted the Qatari ambassador to Russia as saying on Thursday. Qatar is engaged in a diplomatic row with some of its Gulf Arab neighbors, including Saudi Arabia and the United Arab Emirates (UAE). They allege that Doha supports terrorism, a charge it denies. Fahad bin Mohammed Al-Attiyah said in an interview that the talks with Russia on the S-400 systems “are at an advanced stage.” In October, Qatar and Russia signed a military technical cooperation agreement and memorandum of understanding on air defense and military supplies.