India signed a $5.5 billion deal with Russia in 2018 to buy five of its S400 missile systems, initial supplies of which started late last year despite a U.S. law aimed at deterring countries from buying Russian military hardware. India on Wednesday abstained on a UN General Assembly resolution that strongly deplored Russia's aggression against Ukraine, the third abstention in less than a week by the country in the world body on resolutions on the escalating crisis between Moscow and Kyiv.