PRINCETON -- It was a financier-business consultant who cracked first. ''We've been talking here for two hours,'' he said, ''and there have been no trade-offs -- none.'' Around the table, 16 other people nodded their heads in acknowledgment.

Anyone looking at their job titles and knowing that the topic under discussion was national energy policy would have said the lack of agreement was utterly predictable. Gathered at the table in a swank private conference center here were a gas company executive, an independent oilman, the head of a state public-utility commission, a nuclear engineer, a lobbyist for the recreation industry, a housing developer, a coal company officer, the head of an electric utility association, two airline executives, a global environmentalist, a public power lobbyist, two finance executives and a consumer activist.

In seven neighboring rooms were more than 100 other equally mixed participants in the first National Energy Consensus Experiment. Before they came, they had answered individual questionnaires on their preferred energy policies. Morning caucuses of natural allies had refined the list of proposals to some two dozen topics that one interest group or another said it ''must have'' in order to go along with the recommendations.

Now, after a box lunch, each room of negotiators had four hours to determine what, if any, ''packages'' of proposed policy trade-offs they could agree to recommend. The ground rules were tough: a single veto could kill any deal.

''Imagine you are the secretary of energy,'' the professional dispute mediator from Colorado told the group. (I was allowed to observe, on condition that I would not identify anyone by name.) ''You have to put together a package that is economically sensible, environmentally sound and politically salable. Who's got a suggestion?''

The unprecedented exercise was dreamed up by two energy-state governors, George Sinner of North Dakota and Mike Sullivan of Wyoming, and some of their friends in the oil, gas and coal industries. Frustrated by the 15-year impasse in energy policy, they invited all of the other ''stakeholders'' in the energy policy disputes -- traditional antagonists -- to join the war games managed by Larry Susskind, director of the MIT-Harvard Public Disputes Program. Except for the auto industry and organized labor, which rejected invitations, every other interest group decided to send top people to the exercise.

It was tough going. My group chose gas policy as a ''simple'' area to try first. It heard a gas spokesman plead for higher prices to keep producers from going broke -- and shot him down in flames. Other ventures from coal, home-builders and environmentalists fared no better, and halfway through the afternoon, when the financier pointed out the failure to offer any concessions in return for group support of a particular policy, people were looking at their watches and wondering why they'd come.

And then the ice broke, with a consumer activist offering to support four proposals initiated by the electric utilities in return for their agreement to three policies backed by an alliance of consumer and alternative-energy people. In 20 minutes of discussion, the deal was done and ratified by the whole table.

They moved from there to toxics, to auto mileage, to housing -- and suddenly the walls of the room were being papered with sheets of newsprint, outlining their agreements. In the growing euphoria, they even allowed the gas man, who had been their first target, to revive his proposal in modified form and found that it now fit the emerging strategy.

Not all the groups did as well; one or two did even better. Susskind noted the similarity in the dynamics: ''Ninety percent of the agreements were reached in the last 10 percent of the time'' -- a formula familiar to labor-management negotiators.

But these people were old antagonists, dealing with policy questions from nuclear-power licensing to Outer Continental Shelf drilling that have hogtied the policy makers since Three Mile Island and the OPEC oil embargo.

The White House and five Cabinet departments sent observers to the exercise. Officials of the Energy Department, which must recommend a national energy policy to President Bush by the end of the year, said they found the process intriguing and were eager to see the formal summary of agreements.

Deputy Energy Secretary Henson Moore said, ''It's very important in understanding where there can be consensus.'' Department General Counsel Stephen A. Wakefield said, ''I've never heard people be this candid. ... When the stakes are real, they may not be as accommodating, but it gets them focused on the fundamental choice -- whether they continue to veto each other's most important objectives or become part of a process of working out solutions.''

This process of horse-trading goes on constantly among politicians, but in areas such as energy policy, where economic, regional and ideological interest groups are so influential, the result has been deadlock. This was, for many of the antagonists, the first time they had been allowed -- or required -- to negotiate face-to-face.

Even in a simulation, success is enormously heartening.