U.S. Looks to Balance Response to N. Korea

"We got a decent sanctions resolution and we essentially threw it away," said John R. Bolton, President George W. Bush's envoy to the United Nations, who negotiated the sanctions resolution. "The sanctions can and have been effective when you persist. But they don't work if you are constantly turning the light on and off."

North Korea has long sought to separate the United States from the other parties to the six-nation talks, and many of its tactics in recent days appear aimed at that goal.

The Obama administration may have complicated prospects for future negotiations by suggesting that special envoy Bosworth would not be the negotiator at the six-nation talks but that role instead would be filled by his deputy, Sung Kim; Bosworth said in a recent interview that he would handle the bilateral relationships, especially with North Korea.

In response, China and North Korea have signaled that they will downgrade their representation at the talks. But that might leave two key U.S. allies -- Japan and South Korea -- in the lurch, because their bilateral relations with North Korea are at a nadir. Russia is also a participant in the talks.

The administration may have time to fashion an approach because, despite North Korea's defiant vow to restart a plant that makes plutonium, its capacity to add to its small nuclear arsenal is limited by aging technology and by machinery that was disabled as part of a disarmament deal.

Using fuel rods now in storage, North Korea could process enough plutonium for one nuclear weapon within six months, according to expert assessments.

But it would take six to 12 months to restart all facilities at the Yongbyon nuclear plant, and its capacity to produce plutonium is limited to about one bomb's worth of material a year, according to a published assessment by Siegfried S. Hecker, a periodic visitor to the plant and former director of the Los Alamos National Laboratory. Other experts with on-the-ground knowledge said it would probably take much longer for Yongbyon, a Soviet-era facility where maintenance has been neglected, to resume production.

Before North Korea can reactivate Yongbyon, the cooling tower there will have to be rebuilt, according to Cha Du-hyeogn, an expert at the Korea Institute for Defense Analysis, a semi-governmental think tank in Seoul. North Korea blew up the cooling tower last year in an attention-grabbing display of its commitment to abandon its nuclear program in exchange for food, fuel and diplomatic concessions.

Kessler reported from Washington. Correspondent Blaine Harden in Tokyo and special correspondent Stella Kim in Seoul contributed to this report.