But through much of the 1990's, the plutonium program was frozen under an agreement reached with the Clinton administration.

But it did not restart its plutonium program, which by now could have produced more than 50 nuclear weapons.

Uranium enrichment could give the North another way to make nuclear bombs, in addition to its plutonium programme.

But the plutonium program we ended was much larger than the later laboratory effort.

The end of the plutonium program would be mixed news for groups concerned with proliferation.

"It is only probably a matter of months, not years, behind the plutonium" program.

"Yet the rationales and main elements of the Japanese plutonium program have not changed."

Yup, this is the same policy that over the last few months led the North to revive its frozen plutonium program.

North Korea had to therefore freeze its plutonium programme.

They have a vested interest in keeping commercial plutonium programs going, including plutonium-extraction plants working on contract for other nations.