NORTH KOREA'S promise to return to negotiations about the possible dismantling of its nuclear weapons program has the ring of good news. The difficulty is that there is no way for outsiders to know why this enigmatic and brutal dictatorship reversed its previous insistence that it had chosen to become a nuclear power and would no longer bargain over it. Is it because ruler Kim Jong Il finally is prepared to renounce weapons of mass destruction in exchange for economic aid and security guarantees from the West? Or does he merely hope to cash in on South Korea's promise of a massive new aid program, the offer of which seems to have broken the long impasse over the "six-party" talks? Does North Korea intend to set out the terms by which it would give up all of its weapons and nuclear infrastructure -- something it has never done -- or does it want only to avoid being blamed for the absence of negotiations, which might endanger the economic lifeline provided by the South and China?

One set of answers could make the resumption of negotiations a major breakthrough; another could make it merely a new feint in a long game of maneuvering with the Bush administration that has had the effect of providing North Korea with the time and opportunity to build more bombs. A further uncertainty is President Bush's bottom-line position: Would he ultimately agree to grant recognition, a security guarantee and aid to a regime he has rightly described as repulsive? Or is his State Department, which has grown more sure-footed in his second term, merely working to ensure -- as it has in the case of Iran -- that the threat of proliferation rather than the perceived intransigence of the United States becomes the focus of international attention?

In the talks that are scheduled for the last week of July, the United States, Russia, Japan, China and South Korea should press for clear answers from Pyongyang. If the negotiations are doomed to failure, it is past time to embrace other strategies for containing the menace posed by this rogue state, such as more concerted economic pressure by the United States and its allies, or action by the U.N. Security Council. The first and most important test must be whether the North will clearly state its willingness to disclose and dismantle its nuclear programs and provide a formal and detailed response to the proposal the Bush administration made 13 months ago. The administration has been criticized for the supposed parsimony of that proposal, but its basic structure, a progressive exchange of North Korean and U.S. and allied commitments and actions, is sound. Perhaps it could be sweetened -- but the North has yet to accept the underlying premise.

Many officials and experts in and outside the Bush administration doubt that Kim Jong Il would ever agree to give up nuclear weapons. His regime has never offered more than a freeze, and that on only one of its two bomb programs. But should North Korea demonstrate a willingness to negotiate, the president will have to end four years of debate among his aides about whether a deal with one of the world's most criminal and repugnant governments is the best course for U.S. security if it results in the verified dismantling of a nuclear weapons program. It is, as Secretary of State Condoleezza Rice said on Sunday, pointless to have talks with North Korea just to have talks: That only perpetuates a status quo that is convenient for the North but unacceptable to the United States. Yet it is also counterproductive to pursue a strategy of negotiation unless, in the end, the United States is willing to have it succeed.