"The problems start from here," said Japan's chief delegate, Mitoji Yabunaka. "This is the first step, at the entrance. From now starts the work on concrete measures."
There were no breakthroughs in the four-day talks, but diplomats said they agreed to define how the North could move toward disarmament, how such moves could be monitored and what kind of aid the North could expect in return.
One sticking point appeared to be how far North Korea must go to qualify for energy aid and other benefits offered by Washington, which demands that the North dismantle its program completely.
Other participants in the six-nation talks were host China, Russia and South Korea.
"It's difficult to say this round of talks was a big success, but there was some progress, with the United States showing a forthcoming attitude," said Koh Yu-hwan, a professor at Seoul's Dongguk University.
"The talks won't end with one or two more meetings," said Koh. "But I think there will be progress little by little in the future because they were able to make general outlines."
North Korea offered during the talks to freeze its nuclear program in exchange for energy, the lifting of U.S. economic sanctions and its removal from Washington's list of countries that sponsor terrorism.
The North said the freeze would be a step toward eventual dismantling.
But the U.S. proposal requires the North to go further - disclosing all its nuclear activities, helping dismantle facilities and allowing outside monitoring. That plan would withhold some benefits to ensure the North cooperates.
China, the meeting's chairman, said in a statement Saturday that the parties "agreed in principle to hold the fourth round of the six-party talks in Beijing by the end of September 2004."
Lower-level discussions will be held "at the earliest possible date to define the scope, duration and verification ... for first steps for denuclearization," as well as compensation for the North, the statement said.
China canceled a closing ceremony scheduled for Saturday and titled the final declaration a "chairman's statement" rather than a "joint statement" - both signs of how far apart the negotiators were.
South Korea's envoy, Deputy Foreign Minister Lee Soo-hyuck, was optimistic despite the differences. He said the talks involved "substantial discussions" on the competing U.S. and North Korean proposals.
But China's envoy, Vice Foreign Minister Wang Yi, said there were "a number of differences and even opposing ideas" between Washington and Pyongyang, who have no official relations.
"There is still a serious lack of mutual trust," Wang said.
The dispute flared in October 2002, when Washington alleged that North Korean officials admitted their country had a secret weapons program, violating a 1994 agreement.
The United States and its allies retaliated by cutting off the 500,000 tons of free oil they had been giving the energy-starved North each year, among other measures.
North Korea said its freeze offer this week covered all nuclear weapons programs and included a pledge not to make, transfer or test nuclear weapons.
But it said Washington had to take part in providing energy aid - a step that is not in the U.S. proposal.
"If the United States gives up its hostile policy toward us ... we are prepared to give up in a transparent way all plans related to nuclear weapons," a North Korean official said Friday.