North Korean nuclear program sign of 'dark future,' Pentagon chief says

North Korea's progress in developing nuclear weapons is a "harbinger of a dark future," U.S. Defence Secretary Robert Gates said Saturday.

Gates was speaking in Singapore at an annual meeting of defence and security officials. His comments follow North Korea's underground nuclear test last Monday, its short-range missile launches later in the week and its declarations about resuming its nuclear program.

Gates said the North's nuclear program does not "at this point" represent a direct military threat to the United States and he does not plan a buildup of American troops in the region. But the North's efforts pose the potential for an arms race in Asia that could spread beyond the region, he said.

He did not give specifics on how the U.S. might respond to North Korea, but called for tougher sanctions on the reclusive communist regime.

Call for sanctions causing 'real pain'

"For there to be a peaceful solution requires multilateral efforts and a willingness to impose real sanctions that bring real pain," he said.

"The policy of the United States has not changed. Our goal is complete and verifiable denuclearization of the Korean peninsula, and we will not accept North Korea as a nuclear weapons state," Gates said.

U.S. satellite photos have revealed vehicle activity at two sites in North Korea, suggesting the regime may be preparing to launch a long-range rocket, U.S. defence officials told Agence France-Presse.

North Korea fired a long-range rocket from its launch facility at Musudan-ri on April 5. Pyongyang said it carried a communication satellite into space.

The launch failed with the third stage of the rocket failing to separate from the second one, according to U.S. and South Korean defence officials.