U.S. says failure to act on North Korea could be catastrophic

By Michelle Nichols and Lesley WroughtonUNITED NATIONS (Reuters) - U.S. Secretary of State Rex Tillerson warned on Friday that failure to curb North Korea's nuclear and missile abilities could lead to 'catastrophic consequences,' while China and Russia cautioned Washington against threatening military force to solve the problem.While Washington has pressed Beijing to rein in its ally Pyongyang, Chinese Foreign Minister Wang Yi told the U.N. Security Council that "the key to solving the nuclear i