Second Guessing.(North Korea's nuclear arsenal)

The search is on for krypton 85. At this moment American EP3 spy planes are probably sniffing for trace elements of that radioactive particle floating in the atmosphere near the North Korean shore. If they detect any atypical isotopes, the United States will have the chemical "fingerprints" it needs to prove that Pyongyang is making atom bombs.

The North already claims to be doing so. At the end of a week in which nuclear tensions had fallen palpably in Northeast Asia, Pyongyang dropped its latest bombshell. "We are successfully reprocessing more than 8,000 spent fuel rods at the final phase," North Korea's official news agency, quoting an unnamed Foreign Ministry spokesman, declared last Friday, suggesting that its stockpile might already have been largely converted to weapons-grade plutonium.

But, as is often the case with North Korea, nothing is certain. White House and State Department officials say so far there is no evidence that Pyongyang has jump-started its mothballed reprocessing plant. "Our information is inconclusive," says an administration official, "but the best guess is that they're not." Making matters even more murky, Korea experts at the White House say that Pyongyang's statement could be read to mean that North Korea hasn't begun to reprocess the fuel rods but is on the verge of doing so.

Either version is a provocative pronouncement, especially just days before the two sides were meant to sit down in a long-awaited meeting to discuss the North's nuclear ambitions. For experts, the surprise announcement invites two contrasting interpretations. One is that Pyongyang is simply seeking "to raise the stakes and get the United States to respond on their terms" when the three-party negotiations open in Beijing this week, says Derek Mitchell, a senior fellow at the Center for Strategic and International Studies in Washington. By that logic, the North's declaration was intended to temper American -- bravado following its lightning victory in Iraq; it may even have been meant to counter the impression that Pyongyang "blinked" by agreeing to multilateral talks, rather than the one-on-one dialogue it has demanded for months. That the North may be hinting at reprocessing instead of starting secretly suggests a diplomatic--as opposed to military-- agenda.

The other explanation is that ...