The U.S. all-news television network CNN says North Korea has begun fueling a long-range rocket.

Quoting a senior U.S. military official on Thursday, CNN said the fueling signals that the country could be in the final stages of what North Korea says will be the launch of a satellite as early as this weekend.

Other military officials were quoted as saying that the payload atop the rocket appears to have a "bulbous" cover, which could indicate that there is a satellite loaded on the tip.

The report said that although the sources did not know for sure what the payload is, they said there is no reason to doubt that it is a satellite, as indicated by North Korea.

CNN said Pentagon officials are worried less about the payload and more about the launch itself, saying that any kind of launch will give the North Koreans valuable information on how to improve their ballistic missile program.