Kyodo News Agency reported Thursday that working group talks ahead of six-party nuclear negotiations with North Korea will likely be delayed as China is reconsidering its position on the North's possible development of uranium-based nuclear weapons.

Kyodo quoted an unidentified U.S. government official as saying Pakistani nuclear scientist Dr. Abdul Qadeer Khan had briefed Chinese officials on what he had witnessed on his last trip to the stalinist North.

Earlier this week, Dr. Khan said he saw three nuclear devices at a secret underground nuclear plant when he visited North Korea five years ago.

Kyodo quoted the U.S. official as saying that once China arrives at the same conclusion as the U.S. - that the North has been secretly developing weapons based on highly-enriched uranium - Beijing was likely to drastically change its stance towards the North.

Pyongyang has publically denied the existence of a uranium-based program.

Although U.S. officials were unclear about Khan's ability to discern a real nuclear device from a mock-up during his visit, his account, if true would roughly match previous CIA estimates of North Korea's nuclear capabilities.