WASHINGTON — Washington. -- Kim Il Sung, the aged North Korean dictator, has come a long way in seemingly opening his nuclear works to foreign inspection. Still, nobody is yet sure whether Pyongyang has abandoned a nuclear-weapons program or is engaged in a massive deception. In the U.S. government, there is a strong view that the North Koreans may well be cheating. This view was not, apparently, dispelled by the results so far known of an inspection just carried out by the International Atomic Energy Agency.
Experience with Saddam Hussein's Iraq, which was closer to making the bomb than anyone knew until after the Persian Gulf war, was a ''sobering lesson'' for intelligence agencies, as James E. Goodby, a former U.S. arms negotiator puts it. That experience has ensured the greatest caution in assessing North Korea's nuclear intent and capability.
Based on what has come out of IAEA inspections and visits by several U.S. authorities, it appears at this stage that North Korea's extensive Yongbyon nuclear complex may be much farther from building a bomb than advertised in the Central Intelligence Agency's direst assessment. Last February, CIA Director Robert Gates said the Communist country had a continuing nuclear program and was between ''a few months and a couple of years'' from having a bomb.
It clearly does have a gigantic plant at Yongbyon which, if completed, could extract plutonium -- the core material for nuclear weapons -- from spent reactor fuel.
After visiting Yongbyon facilities last month, the first foreigner to do so, the IAEA director, Hans Blix, said the plant in question was 80 percent complete with 40 percent of its equipment installed. Completed, he said, it could serve as a plutonium-reprocessing plant. His inspectors followed later and are still examining the data they gathered.
North Korean achievement of nuclear arms, or even unqualified evidence that it was heading successfully in that direction, would send shock waves through Asia, possibly triggering a nuclear race.
But there is wide disagreement on the North Korea's present aims, and Pyongyang of course steadily denies any nuclear-weapons ambition.
* James Lilley, assistant defense secretary for international security affairs and former U.S. ambassador to China, recently told reporters the North Koreans were ''engaged in a [weapons] program and trying to obscure it from us.'' There was ''fragmentary evidence'' that they were moving plutonium-making capabilities underground and this would be very hard to track.
* Selig S. Harrison, of the Carnegie Endowment's nuclear-weapons study group, reached this ''hypothesis'' after a late April-early May visit to North Korea: The government pursued nuclear arms, ''but didn't get very far.'' It decided to give up. Its economic survival required ending its isolation and opening up to the West. There was no hope of that unless nuclear-weapons goals were abandoned.
* Leonard S. Spector, a leading authority on nuclear proliferation, who was with Mr. Harrison in North Korea, came home ''more agnostic'' than his colleague, apprehensive about reports of hidden stocks of nuclear-weapons material and the possibility, at least, of ''massive cheating.''
* William J. Taylor of the Center for Strategic and International Studies, who spent a week traveling and conferring with high officials in North Korea earlier this year, says the ''weight of evidence'' is that North Korea has had a nuclear-weapons program. But there is ''no conclusive evidence anywhere'' that a bomb had been produced. If critical facilities have been hidden underground, they will be found.
This is enough to demonstrate how speculative and controversial the issue of North Korean nuclear arms can be.
A crucial point will come, Mr. Spector says, when IAEA inspectors determine whether the records of the operation of a small reactor are consistent with what the CIA says, or whether they support differing North Korean claims. The CIA, based on satellite observations, believes the reactor has produced a stockpile of nuclear-weapons material from which plutonium could be extracted. The North Koreans say the reactor, 6 years old, has had operating problems and still has its initial fuel load.
Most critics, whatever their view on an arms program, support the carrots-and-sticks policy being followed by the United States, Japan and South Korea to get Pyongyang to give up its nuclear program in return for a chance to reap badly needed economic benefits.
Mr. Goodby, a longtime foreign-service officer, says a worst-case analysis is usually prudent based on North Korea's history. But he points out that the country faces a dramatically changed situation through the loss of its major ally, the Soviet Union.
Moreover, it has reached agreement with South Korea on the aim of de-nuclearizing the peninsula and conducting no-notice inspections, though it would be wrong to expect quick results.
North Korea ''will try to break out of its isolation,'' he argues. And ''the U.S. policy is correct -- insistence on [North Korea's] abandoning any pretensions to becoming a nuclear power.''