UN Secretary General Ban Ki-moon today welcomed the signing in Prague of a new nuclear reduction pact by leaders of the United States and Russia, according to dpa. The signing of the new START Treaty represented an "important milestone in the international efforts to advance nuclear disarmament and to achieve a world free of nuclear weapons," Ban said in a message. The new treaty would help create a "positive atmosphere" for the UN conference to review the Nuclear Non-Proliferation Treaty in New York in May, Ban said. "I commend President Dmitri Medvedev and President Barack Obama for their leadership," Ban said.