NEW YORK, SEPT. 26 -- Secretary of State James A. Baker III and Soviet Foreign Minister Eduard Shevardnadze vowed today to mount a new effort to accelerate the negotiations on reducing strategic nuclear arms and conventional forces in Europe, according to participants in their discussions here.

Both areas of arms negotiations have been languishing in recent months despite a commitment by President Bush and Soviet President Mikhail Gorbachev to complete them by year's end.

Prompted by the specter of Iraq obtaining nuclear weapons, Baker and Shevardnadze also agreed to try to make nonproliferation a major arms-control issue for the rest of the decade, the participants said.

Baker outlined to Shevardnadze some flexibility in the U.S. position on conventional talks in hopes of getting a positive response this week.

The two ministers are under growing deadline pressure to get action on the arms control treaties. The United States and some of its allies have said the conventional forces agreement must be completed before they will attend the 35-nation European summit scheduled for Nov. 19 in Paris. Both Bush and Gorbachev said at their June summit in Washington they would finish the strategic arms reduction treaty by year's end, and the Soviets have expressed interest in a December summit in Moscow to sign the agreement.

But both negotiations have been buffeted by the rapid pace of change in Europe and in the Soviet Union. U.S. officials have said they believe the Soviet leadership has been distracted by the turmoil at home and that arms control negotiations also have been slowed because of caution and disenchantment in the Soviet military, which faces major troop cuts and painful decommissioning. Soviet military leaders, in addition to the problems of retrenchment from Europe, have reportedly balked at making new arms control concessions to the United States. At the same time, some U.S. proposals have also proved to be stumbling blocks with Moscow.

Both sides appeared interested in moving ahead today, according to Soviet and U.S. sources. Baker and Shevardnadze, accompanied by teams of arms control negotiators, agreed to hold another meeting Friday and may work through the weekend in an effort to clear some of the bottlenecks, officials said. In particular, the officials said, there is a desire by both sides to speed up the conventional arms talks. Foreign ministers from the 35-nation Conference on Security and Cooperation in Europe (CSCE) are to meet here next week.

British Foreign Secretary Douglas Hurd said today that without a conventional arms treaty there would be no summit. The treaty is supposed to be signed at the summit.

Shevardnadze brought some new proposals on strategic arms to the discussions, the Novosti Information Agency reported tonight. Quoting senior Soviet sources, the agency said Shevardnadze came prepared to propose a new lower ceiling on the Backfire bomber operated by the Soviet air force. The United States has been seeking a Soviet commitment to a firm ceiling on Backfires in a side agreement to the treaty. The Soviets had previously offered to provide a commitment not to give the bomber intercontinental range, but such a proposal for a ceiling would appear to be a concession.

The talks among experts, as well as between Baker and Shevardnadze, are also expected to focus on the issue of U.S. agreements to share nuclear weapons with Britain. The Soviets have been seeking to proscribe future transfers of strategic weapons from the United States to its allies, such as Trident submarine missiles to Britain, while the Bush administration has proposed that the pattern of cooperation in the past be allowed to continue, including the development of a new air-to-surface missile. The Soviets are expected to continue to insist that future cooperation be limited to submarines and not extend to other weapons programs.

Meanwhile, the Pentagon announced today that the United States, in anticipation of the conventional forces treaty, would begin reducing U.S. troops in Europe next year by 40,000. Defense Secretary Richard B. Cheney said the reduction is an attempt to respond to "changing security requirements" and budget cuts. Analysts noted that the cut is about half what the United States would have been forced to pull out under troop limits that had been under discussion in the conventional forces treaty.

Recently, both Washington and Moscow agreed to leave troop limits for future negotiation. A Soviet negotiator has said, however, that Moscow is still interested in limits on U.S. forces in Europe, and today's announcement may have been intended as a gesture in that direction.

Baker and Shevardnadze also spent a considerable amount of time today on aircraft limits, which have become a major sticking point in the conventional forces talks. A senior State Department official said the United States is still pushing for an agreement on aircraft, although there has been speculation that, like troop limits, the issue might be removed from this treaty and addressed in later negotiations.

"We are interested in making it a part" of the treaty "if we can," the official said.

The senior State Department official said Baker and Shevardnadze had a discussion on ways the superpowers could improve nuclear and chemical nonproliferation efforts in the years ahead. The official said they wanted to make nonproliferation "a new arms control agenda . . . for the '90s." The official added that "Iraq provides a springboard" for a stronger effort to control the spread of weapons of mass destruction. By most estimates, Baghdad is two to five years from being able to develop an atomic bomb.