MOSCOW, Dec 6 (Reuters) - Russian Foreign Minister Sergei Lavrov said on Monday a deal to supply India with S-400 air defence missile systems was being implemented despite what he said were U.S. efforts to undermine the accord. Speaking at a news conference in India, Lavrov said India had made clear that it was a sovereign country. The deal with Moscow puts India at risk of sanctions from the United States under a 2017 U.S. law aimed at deterring countries from buying Russian military hardware. read more