The report could influence the ongoing six-party talks in Beijing over North Korea's alleged nuclear weapons program.

Clues to the possible joint nuclear test followed underground nuclear tests carried out by Pakistan in May 1998, the paper said.

According to the sources, a US military jet sent to sample the air over Baluchistan, Pakistan, after the final nuclear test found traces of plutonium, which surprised US experts since Pakistan had openly stated that it was testing bombs fueled by highly enriched uranium.

The explanations for the plutonium included the possibility that North Korea could have given Pakistan some of its plutonium to conduct a joint test of an atomic weapon, the sources said.

The matter was debated but never settled and was mostly forgotten until Pakistani scientist and architect of the country's atomic bomb, Abdul Qadeer Khan, confessed last month that he passed nuclear technology on to North Korea, Libya and Iran.

The daily said the plutonium North Korea may have provided Pakistan for the joint test could have been a form of compensation for Khan's assistance.

If the joint Pakistani-North Korean nuclear test in 1998 is confirmed, it would strongly suggest that North Korea can not only produce plutonium but also build a weapon it has claimed it possesses, the daily said.

The US Central Intelligence Agency, US officials told The New York Times, has been urgently preparing a report this week on what North Korea may have gained from its dealings with Khan.

WAR.WIRE