Russia Urges Pact on Faster Nuclear Cuts : Arms: Accord is sought before June summit. Baker, Kozyrev still disagree on key issues.

Russia challenged the United States on Wednesday to agree to faster cuts in long-range nuclear weapons in time for the June summit between President Bush and Russian President Boris N. Yeltsin.

After almost five hours of negotiations on the two presidents’ competing arms reduction proposals, Secretary of State James A. Baker III and Russian Foreign Minister Andrei V. Kozyrev said they made progress but still disagree on several key issues.

Bush and Yeltsin have both proposed massive cuts in their nuclear arsenals, but they differ on what missiles should be cut and how fast. Kozyrev said he is optimistic that a compromise can be reached by the summit, scheduled for Washington on June 16 and 17.

“We worked as friends and allies standing on one side of the barricade, with all the problems that beset us on the other,” he said.

Both sides agreed on the principle of much deeper cuts in nuclear missiles but disagreed over how fast the cuts should be made.

“The primary differences between us now continue to relate to the timing of future reductions,” Baker said. “The timing has not been agreed to, nor, frankly, has the exact mix that those reductions would take.” He said the two countries are exchanging proposals to solve the issues.

Kozyrev indicated that Russia is pressing for an American commitment to deeper reductions of multiple-warhead missiles within the seven-year timetable of the Strategic Arms Reduction Treaty.

“The time frame is different,” he said. “We are looking for ways and means of bridging the gap between us, including a means of enhancing the reduction of MIRV (multiple warhead) missiles within the time frame provided for by the START treaty.”

In his State of the Union address in January, Bush proposed a cut of about 50% below the limits imposed by the START treaty, to roughly 4,500 nuclear warheads on each side. But at the same time, Bush asked Yeltsin to give up all multiple-warhead land-based missiles, the most dangerous part of the Russian arsenal.

In a counteroffer the next day, Yeltsin proposed deeper cuts, to 2,500 warheads or fewer. But he also insisted that a ban on multiple-warhead missiles should apply to U.S. nuclear submarines--the heart of the American nuclear deterrent--as well as Russia’s land-based force.

That disagreement remains, Kozyrev and Baker said. But their comments to reporters here indicated that they are now discussing specific ways to combine the two proposals--a significant step forward.

Senior U.S. officials said, for example, that they are willing to accept the principle of cuts in the U.S. nuclear submarine force. But they want to see cuts in Russia’s land-based missiles first. U.S. strategists consider the Russian missiles the most “destabilizing” in the arsenal because they are relatively vulnerable to attack--thus, in a crisis, leaders might be tempted to fire them rather than risk losing them.

Submarine-based missiles, they argue, are less vulnerable--and thus less likely to be used.

But Russian military officials are said to be unhappy about the idea of cutting their most powerful missiles first.

Kozyrev’s comments appeared to suggest a compromise in which Russia might agree to early cuts in its land-based multiple-warhead missiles as long as the United States made a firm commitment to cuts in submarine-borne missiles within seven years.

All the reductions under discussion would go far beyond the START treaty, which was signed last July but has not yet been ratified by the Senate or implemented by either side.