OSAKA — In addition to compelling North Korea to scrap its nuclear weapons program, Japan and the United Sates must force it to account for all of its uranium and plutonium, one of America’s top nonproliferation experts said Tuesday.

“There might be enough nuclear material in North Korea, material that is unaccounted for by the International Atomic Energy Agency, to make one or two nuclear bombs,” Lawrence Scheinman said during a visit to Osaka.

Scheinman served in the administration of President Jimmy Carter and is now a professor at the Washington-based Center for Nonproliferation Studies. In an interview with The Japan Times, he noted that North Korea remains an enigma.

“You have to stop and ask why they decided to admit that they had a nuclear weapons program,” he said. “It’s inconsistent with their past (secretive) behavior.”

Scheinman offered three possible motives:

North Korea feels threatened by President George W. Bush’s “axis of evil” reference in January.

Its political and economic systems have failed and is desperate for international aid.

It feels it has a security problem, being flanked by South Korea and Japan, which are under the U.S. defense umbrella.

“North Korea wants to be taken seriously. Admitting to a nuclear weapons program is one way to accomplish this goal,” Scheinman explained.

A former adviser to the IAEA, Scheinman said figuring out what the agency should do once its inspectors are permitted back into North Korea is the easy part. The problem now is how to get them back in.

“I see two camps emerging in Washington. The first camp says, ‘Tell them what to do. Put the squeeze on and stop sending heating oil,’ ” he said.

Some in this camp also advocate denying humanitarian aid, Scheinman added, even though such a move would hurt ordinary North Koreans.

“The other camp says to proceed more slowly, and stick with the previous agreements. Which camp will win out is as yet unclear.”

Scheinman insisted, however, that the most important goal is for the United States and Japan to convince North Korea to let the IAEA go back in and do its job.

“Japan and the United States must be firm in insisting North Korea abandon its nuclear weapons programs,” he said.

“But they also have to make sure the IAEA monitors North Korea in shutting down its uranium enrichment plant.”

Scheinman believes the use of military force to accomplish this goal is not an option. North Korea, he said, is not Iraq.

“Iraq and North Korea are different for three reasons. First, the neighborhood is different. A U.S. strike against North Korea would have major repercussions in South Korea and Japan.

“Second, the U.S. is already engaged on two fronts, one against the war on terrorism, and another against Iraq. There are grave doubts if the U.S. can handle a three-front war.

“Third, and most importantly, North Korea has admitted to its weapons program, and that they cheated on their international agreements. Iraq is still in a state of denial,” Scheinman said.