In a press conference that bordered on jovial, Secretary of State Colin Powell and his Russian counterpart Igor Ivanov on Friday called talks on reducing long-range nuclear weapons "successful," though no agreement has been finalized.

"We came down an hour early because we finished our work an hour earlier, and regret any inconvenience that may have caused the press," Powell said with a laugh after reporters scrambled to assemble for the conference.

The two leaders spent their two days of talks discussing details for a presidential summit in Russia later this month. At the summit, the Russian and U.S. leaders hope to sign an agreement that cuts nuclear weapons caches from more than 6,000 each to between 1,700 and 2,200.

"I think it's going to be a very, very successful summit," Powell said, reporting that they had "made progress toward the completion of our work on a strategic framework document. There are still some outstanding issues, but I think I can say that we're both encouraged by the progress that we made today."

An official speaking on condition of anonymity said substantial progress was made on how to verify reductions in arsenals of long-range nuclear warheads.

Pressed for details on what had been worked out and what was still up in the air, Powell wouldn't budge. The lingering sticking point for Russia is concern that the United States does not want to destroy the warheads, merely de-activate them and stick them in storage.

President Bush has said he intends to reduce the U.S. long-range nuclear arsenal regardless of whether Russia reciprocates. Putin has said Moscow would be willing to cut the Russian arsenal even deeper — to 1,500 warheads.

Powell said the "remaining differences are there, and we need to spend more time working on them and discussing them to see if we can resolve them in time for the Moscow summit. If we can, fine. And if we're unable to, the work will continue. But I am encouraged."

The secretary said it hadn't been decided yet whether the document prepared for presidential signatures would be a treaty or an executive order. Both are legally binding in international law.

A treaty would require approval of two-thirds of the Senate. An executive order would need the approval of a majority of the House and Senate.

Ivanov also termed the talks "very constructive", saying "on many issues we achieved substantial progress."

But he didn't give details of the progress either, sticking to generalities and positive spin.

"We're interested in maintaining between our countries, between Russia and the United States, relations with partnership, predictability and constructiveness," Ivanov said through a translator. "And we expect that the upcoming visit of the U.S. president to Russia, his negotiations with the president of the Russian Federation, and the agreements that will be reached, will contribute to reaching this goal."

Determined to proceed with an elaborate anti-missile shield, President Bush opted out of a 1972 treaty that outlawed national defenses against missile attack. Russia objected, but has muted its criticism on the point.

Still, the Russians wanted to include in the agreement an opening for negotiations over missile defenses, but the United States said no and that debate is over, the senior U.S. official said.

Powell and Ivanov are due to meet again at the spring session of the NATO alliance in Iceland May 14-16 and negotiations could go right up to the eve of the May 23 summit.

Also that week, Undersecretary of State John Bolton will meet in Moscow with Russian Deputy Foreign Minister Georgy Mamedov.

The Associated Press contributed to this report.