Progress has been made towards answering suspicions North Korea tried to enrich uranium for atom bombs but the issue is by no means solved, the chief U.S. negotiator on Pyongyang's nuclear disarmament said on Wednesday.

Christopher Hill was speaking after talks with Mohamed ElBaradei, director of the watchdog International Atomic Energy Agency (IAEA) which has monitors in North Korea verifying the process to disable Pyongyang's nuclear weapons program.

ElBaradei said the six-party deal to dismantle the program by the end of 2007 was moving in the right direction.

The Washington Post reported on Saturday that North Korea was offering Washington evidence that it had never intended to refine uranium for atomic bomb fuel parallel to its known production of plutonium for warheads.

Quoting unnamed South Korean and U.S. officials, the paper said Pyongyang was granting U.S. experts access to equipment and documents in confidential talks to beef up its case that there was no clandestine enrichment effort.

I can say we have made some progress but by no means have we solved the issue up to now, Hill, the assistant secretary of state for East Asia and Pacific affairs, told reporters.

We are continuing to work with them to resolve the matter. I don't think it's very helpful to get into details at this point. We are very much in the middle of a process, he said.

But I think (North Korea) understands very well that this matter must be resolved to mutual satisfaction.

COMMITMENT TO FULL DISCLOSURE

The six-nation agreement requires North Korea to disable its three key nuclear plants by the end of 2007, provide a list of all nuclear arms activity, account for all its fissile material and answer U.S. suspicions of a clandestine enrichment drive.

In exchange, the destitute Stalinist country will receive 1 million tonnes of heavy fuel oil or equivalent aid and steps to end its international isolation.

They have shown us some things, and we are working it through, the Washington Post quoted a unidentified senior U.S. official as saying regarding the enrichment issue. Some explanations make sense; some are a bit of a stretch.

It quoted an unnamed South Korean official as saying North Korea was trying to show that materials it had imported had been intended for conventional weapons programs and other dual-use projects, not for nuclear weapons.

The Washington Post said Pyongyang was hoping Washington would lift its sanctions against the reclusive Communist state when Pyongyang makes the declaration as part of the disclosure of its nuclear activities.

The Bush administration branded North Korea part of an axis of evil and accused it in 2002 of seeking to enrich uranium to the high level required for the core of nuclear weapons.

The U.S. charges of a large-scale uranium program ended a 1994 Clinton administration agreement that had frozen a North Korean reactor that produced plutonium. Either plutonium or highly enriched uranium can be used to produce nuclear weapons.

Hill also said the five powers dealing with North Korea -- including Russia, China, Japan and South Korea -- expected to get a list of Pyongyang's nuclear materials and equipment soon.

We want to make sure this list is very complete and we will be working very closely with the IAEA on that matter, he said.

U.S.