Ng Han Guan/AP Photo

North Korea is expected to launch a long-range rocket in the next 24 to 48 hours, according to a U.S. official.

The official says that based on the amount of fuel the North Koreans have pumped into the rocket, the trajectory could be very long. The rocket is now expected to travel south by southeast, crossing over the Philippines and, if successful, splashing down in waters not far from Australia.

Many of the countries along the route have asked for U.S. assistance in tracking the missile's trajectory, which has sophisticated radars and a number of antiballistic missile ships in the region.

The White House and the State Department have stayed in close contact with Asian nations.

The primary focus, however, has been putting pressure on China to rein in North Korea, which thus far has shown little willingness to cooperate. "It is fair to say that the Chinese are spending most of their time telling the U.S. to relax," the official said.

But the missile launch is not expected to end the provocation by North Korea. Officials fear a nuclear test will soon follow. Large amounts of dirt and ground cover are being moved at one of North Korea's nuclear sites, which experts believe indicates the North Koreans will test a nuclear device once the rocket test is complete. Even more alarming is that officials believe that, unlike the first two nuclear tests North Korea conducted with plutonium, this one could be a uranium device, which would indicate a secret uranium facility.

White House press secretary Jay Carney said Tuesday that the U.S. was continuing to work with its international partners.

"The proposed missile launch, if conducted, would represent a clear and serious violation of North Korea's obligations under two United Nations Security Council resolutions that explicitly prohibit North Korea from testing ballistic missiles," Carney said.

North Korea claimed the planned rocket launch is just a satellite called Shining Star being put into orbit to celebrate the 100th anniversary of the birth of the regime's founder, Kim Il Sung. Experts do not doubt there is a satellite attached to the rocket, but feel it is just cover to test a long-range missile that could be capable of hitting the U.S.