A U.S. State Department spokesman said Wednesday that Washington is willing to take part in next week's six-party talks on the North Korean nuclear standoff despite Pyongyang's continued denial to having a nuclear weapons program based on highly enriched uranium (HEU).

Spokesman Richard Boucher reiterated during a regular press briefing the U.S. willingness to attend the talks without conditions.

In addition to a plutonium-based program, the U.S. believes the North has an HEU program and wants the communist state to admit as much at the upcoming six-party talks, set to open in Beijing on Feb. 25.

North Korea has denied American allegations it admitted to a visiting U.S. delegation in 2002 that it was running a secret HEU program. However, the denial has been undercut by a recent confession of a Pakistani scientist that he had transferred nuclear technology to the North in the past.

Earlier on Wednesday, U.S. Undersecretary of State John Bolton warned that North Korea's denial could derail Washington's commitment to resolving the nuclear crisis peacefully.

Boucher reiterated Washington's goal to effectuate a complete, verifiable and irreversible end to the North's nuclear weapons programs. He added, such an end "can't be complete if [the North Koreans] don't acknowledge half their program."