Gates: North Korea Prepared to Launch Missile Capable of Hitting Alaska

North Korea is set to test-launch its most advanced missile, one capable of delivering a nuclear payload to Alaska -- a threat not felt by the U.S. since the end of the Cold War.

Defense Secretary Robert Gates, who is in the Philippines Monday discussing the region's military and security issues, said Pyongyang appears to be preparing to launch an intercontinental ballistic missile -- or ICBM -- a projectile with a range of more than 4,000 miles.

But Gates stopped short of saying the reclusive communist regime had plans to target Alaska -- or any region within the United States.

"At this point, it's not clear what they're going to do," Gates said at a Manila news conference with Philippines Secretary of National Defense Gilberto C. Teodoro Jr. on Monday.

Pentagon officials said satellite images have detected activity at a newly constructed missile site on North Korea's west coast -- a site similar to facilities used in Iran. The imaging shows the long-range missile propped up and ready for launch.

A U.S. official told The Associated Press that satellite images and other intelligence the missile was moved by train, but he did not comment on where it was moved to. Yonhap news agency in South Korea reported that it went to the new Dongchang-ni facility near China.

Yonhap said Pyongyang could be ready to fire it within the next week. But the U.S. official says it could take longer than that.

Gates stressed that the administration must pursue diplomacy with U.S. allies in the region before it considers taking military action. Secretary of State Hillary Rodham Clinton has telephoned the Russian and Chinese foreign ministers on Monday to get a tough U.N. condemnation of North Korea's missile and nuclear tests.

State Department spokesman Robert Wood said the U.S. wants North Korea to return to stalled six-party disarmament negotiations, but the Obama also administration wants a "strong, unified" message sent to North Korea that its "belligerent" actions have consequences.

Asked if the U.S. was reconsidering its approach to the North, Wood said that "because things haven't worked doesn't mean you don't keep trying."

North Korea tested a long-range missile in April, but other launches over the last week have been only short-range.

South Korean media have speculated that the North wants to time the launch for around June 16, when South Korean President Lee Myung-bak has a summit in Washington with President Obama.

FOX News' James Rosen and the Associated Press contributed to this report.