As the United Nations prepares for a possible vote on North Korean sanctions, U.S. officials say they have found evidence of radioactivity from the reclusive state consistent with a nuclear explosion.

U.S. officials, speaking on the condition on anonymity, say preliminary analysis shows radioactivity in air samples collected near the suspected North Korean nuclear test site. Earlier Friday, U.S. officials said they had not found any evidence to prove North Korea had detonated a nuclear device last Monday as claimed.

A Vienna-based nuclear monitoring body, Comprehensive Test Ban Treaty Organization, says it has yet to find radioactivity in air samples taken after the North Korean test, but it says that does not rule out that a nuclear test was conducted.

Meanwhile, U.N. diplomats say last-minute Russian and Chinese objections to a compromise draft resolution against North Korea are raising fears Saturday's scheduled vote may be delayed.

The resolution includes economic and weapons sanctions against North Korea, including a travel ban and financial restrictions. It specifically rules out the use of force in what is seen as a concession to China and Russia.

In other developments, Russia's Itar-Tass news agency quotes Russia's deputy foreign minister, Alexander Alexeyev, as saying in Pyongyang that North Korea is open to returning to the six party talks on its nuclear program in the near future.

In Washington, President Bush signed a law allowing the United States to impose sanctions on any foreigner who provides weapons technology to North Korea.

And the Non-Aligned Movement of 118 developing nations added its voice to the growing condemnation of North Korea Friday, urging Pyongyang to adhere to the group's disarmament goals. North Korea is a member of the Non-Aligned Movement

North Korea is threatening to carry out more nuclear tests. Pyongyang has said it would regard any tough new sanctions as a declaration of war.

Some information for this report provided by AP, AFP and Reuters.