By ANITA CHANG
The Associated Press
Thursday, August 16, 2007; 8:34 PM

SHENYANG, China -- Envoys from six nations discussed on Thursday how to implement a February agreement by North Korea to make a full declaration of its nuclear program and begin disabling it.

Envoys to the six-party working group talks said they expect progress even though disagreements remained between the North and the other five countries involved _ the U.S., China, South Korea, Russia and Japan.

The North agreed with those five countries in February to make a full disclosure of its nuclear program and to dismantle its nuclear facilities in exchange for energy aid.

"This is a tough phase because this is the phase that takes us beyond where we've been before, beyond just shutting down the facilities," chief U.S. nuclear envoy Christopher Hill said Thursday after the first of two days of talks. "But we have to come up with common definitions so that we are satisfied when they say they are disabling, we know what they're doing and we agree that it's disablement."

Optimism has been building since North Korea shut down its sole operating nuclear reactor last month, with the leaders of the two Koreas to hold their first summit in seven years on Aug. 28-30.

The U.S. and North Korea were expected to meet at the end of this month or early next month to discuss normalizing relations, something the North has long been pressing for. No date or venue has been set.

Hill said the North Koreans were committed to holding up their end of the February pledge.

The working group meeting in this northeastern Chinese city was the latest step in the denuclearization plan after the North shut down its reactor.

But Japanese delegate Akio Suda told reporters after Thursday's talks that uncertainties remained about North Korea's stance.

"They explained what they are thinking now, but what they said was unclear so we have to talk more technically," he said.

Hill said the problems involved the definition of disablement, but declined to discuss specifics.

The U.S. envoy also said the North Koreans have addressed their willingness to resolve the country's alleged uranium enrichment program.

Washington accused the North in 2002 of embarking on such a program in violation of an earlier disarmament deal _ touching off the latest nuclear crisis. North Korea tested a nuclear bomb in October last year.