Claiming to be a "full-fledged nuclear weapons state," Pyongyang said it wanted the talks, involving the United States, the two Koreas, China, Russia and Japan, transformed into a disarmament forum to tackle what it called the US nuclear threat to the Korean peninsula.

"We'll study it (the statement) carefully. We're starting to look at it now. It's not really clear what they mean," State Department spokesman Richard Boucher told reporters.

He wondered whether North Korea was putting up new conditions for talks.

Pyongyang boycotted the talks after attending three rounds, blaming US "insincerity."

Boucher reiterated that the goal of the talks was denuclearization of the Korean peninsula. "That's true and that's something everybody's accepted," he said.

"But we've also made clear that people need to return to talks without preconditions. The way to achieve denuclearization on the peninsula is for all the parties to get together and sit down and work this out through the six-party talks.

"That's the place to do it. That's the best opportunity to achieve that goal and to end North Korea's nuclear ambitions through a process of peaceful diplomacy. And so once again, we urge the North Koreans to return to those talks without preconditions," he said.

North Korea wants future talks to focus on ways "to completely remove the US threat of nukes and a nuclear war from the peninsula and its vicinity," Pyongyang's foreign ministry spokesman said Thursday.

The talks, he added, should provide "a platform for seeking comprehensive ways of substantially and fairly realizing the denuclearization of the peninsula, not just as a bargaining ground where a give-and-take-type way of solution is discussed."

The nuclear standoff erupted in 2002 when the United States accused the North of operating a secret uranium-enrichment program.

Washington believes North Korea possesses one or two crude bombs and may have reprocessed enough plutonium from spent fuel rods at its Yongbyon nuclear complex for half-a-dozen more.