Moscow, Jan 31 : Ukraine's admission to the North Atlantic Treaty Organization (NATO) would seriously undermine relations between Russia and the alliance, Russian Foreign Minister Sergei Lavrov has said. "Everyone understands that Ukraine is not ready (to join NATO) and will not make any contribution to strengthening NATO's security," Lavrov told a Russian TV programme. Commenting on statements that NATO is defensive, the top diplomat recalled how the US-led military bloc "bombed Yugoslavia for almost three months, invaded Libya in violation of a UN Security Council resolution, and behaved in Afghanistan", Xinhua news reported. Lavrov reiterated "the indivisibility of security," the principle that no state should strengthen its own security at the expense of others. He said that Russia is sending official requests to the member countries of NATO and the Organization for Security and Cooperation in Europe, urging them to explain what they intend to do under this principle. /IANS