Russian President Vladimir Putin warned of a global catastrophe unless a diplomatic solution is reached over North Korea. <br/><br/>Speaking to reporters in the Chinese city of Xiamen following a summit of the five-nation BRICS club of emerging economies yesterday, he also rejected US calls for more sanctions as "useless. <br/><br/>His comments appeared to draw the lines for a clash at the United Nations pitting Moscow and Beijing against Washington and its allies.<br/>US on Monday demanded the "strongest possible measures" against North Korea for detonating what Pyongyang said was a hydrogen bomb that could be mounted on a missile.<br/><br/>South Korea and Japan, plus permanent Security Council members France and Britain, have called for stronger measures against North Korea, with several arguing for a potentially crippling oil embargo.