U.S.-Soviet negotiations on a new treaty reducing strategic nuclear arms have ground to a virtual halt due to lingering disputes over more than a dozen issues, raising fresh doubts that the accord will be completed as promised by the end of the year, according to senior U.S. and Soviet officials.

After agreeing months ago on most of the key arms limitations, Moscow and Washington have been unable to settle squabbles over matters such as the potential reuse of nuclear warheads from scrapped weapons, the transfer of arms and military technology developed by the United States to Britain and aspects of the U.S. Strategic Defense Initiative (SDI) research program, the officials said.

Nor has progress been made on further reductions of large Soviet missiles and limitations on the Soviet Backfire bomber, issues that were unsuccessfully tackled during the U.S.-Soviet summit meeting in Washington nine weeks ago. The two sides also disagree about various intrusive measures for monitoring compliance with the new accord.

The officials expressed concern that the negotiating difficulties have not received the high-level attention required to achieve breakthroughs, partly due to the distraction provided in both capitals by Germany's unification, internal Soviet political turmoil and other world events that have impinged on superpower security concerns.

A senior U.S. official predicted this week that the arms treaty could be imperiled if the current negotiating deadlocks delay its completion for more than three to six months.

After that, he said, politicians might consider the accord obsolete due to warming superpower relations, sharp military budget cuts in both countries and a growing sense that the threat of nuclear conflict has declined.

But U.S. officials argue that regardless of how warm their relations become, the superpowers still need a mechanism for balanced, deep reductions in the most threatening nuclear weapons on each side.

Despite accommodation on regional crises such as Iraq, both governments are still protecting narrow military interests as the eight-year-old strategic talks head into the final stretch, the U.S. and Soviet officials said.

They urged scheduling of a special meeting of U.S. and Soviet foreign ministers or a presidential summit on arms control later this year, an idea that was discussed but not agreed by Secretary of State James A. Baker III and Soviet Foreign Minister Eduard Shevardnadze in consultations last week.

Presidents Bush and Mikhail Gorbachev pledged last December to complete the new accord this year, forcing a reduction of roughly 20 percent to 30 percent in strategic, or long-range, nuclear arsenals to be carried out over the next seven years.

Barring further negotiated reductions or budget-related weapons cuts, each side would then have 7,500 to 10,000 warheads capable of hitting each other's territory, each detonating with far greater force than the weapons that devastated Hiroshima and Nagasaki in World War II.

The officials, providing details of the confidential Geneva talks on condition that they not be identified, said one of the most difficult issues concerns the fate of hundreds of ballistic missiles and thousands of associated nuclear warheads that must be withdrawn from U.S. and Soviet arsenals under the accord.

They said both sides are eager to avoid completely scrapping this weaponry, which cost billions of dollars, particularly when military budgets are tight. But they disagree sharply over what restrictions should be placed on any alternate, "peaceful" uses.

U.S. negotiators, for example, favor allowing such missiles as the aging Minuteman II and the Poseidon to be used for launching space weapons or as targets for testing the SDI program, aimed at developing a partial defense against Soviet nuclear attack.

The United States also has proposed to exempt any missiles involved in SDI tests from a treaty provision inspired by the United States requiring the open transmission of electronic information during any missile flight tests.

The Soviet Union, in contrast, favors using such missiles only for launching "peaceful" satellites or other non-weaponry space objects, and opposes any use in connection with SDI, a program it has long opposed.

The Soviets also say the new strategic accord should follow the practice of the 1987 accord on Intermediate-Range Nuclear Forces (INF), which barred the use of any scrapped medium-range and shorter-range missiles "as a target vehicle for ballistic missile interception."

The two sides remain at odds over the potential reuse of nuclear warheads withdrawn under the new accord, an issue that caused the Reagan administration considerable embarrassment during 1988 Senate deliberations on the INF Treaty. Sen. John Glenn (D-Ohio) said then that he "found an appalling number of people I talked to . . . who were not aware that this {INF} treaty does not destroy one single nuclear explosive device" and, along with several other legislators, complained that it should.

U.S. officials say the Bush administration nonetheless had decided to oppose any limitations on reusing nuclear warheads withdrawn from U.S. and Soviet arsenals on remaining strategic weapons.

They say a potential shortage of nuclear weapons materials and the shutdown of a weapons production plant at Rocky Flats, Colo., could force the reuse of intact warheads from retired, Trident I missiles atop newer, as yet undeployed Trident II missiles on strategic submarines.

The Soviets, in contrast, favor retaining the somewhat more restrictive formula of the INF accord, which required the destruction of the exterior warhead shell, but allowed retention of the "guidance elements" and mechanical guts of the warhead, including associated fissile materials.

Soviet officials say they fear complaints from the Supreme Soviet, a newly empowered legislative body that must approve the accord, if warheads can be reused intact.

Moscow and Washington also have not been able to agree on U.S. sales of strategic weaponry to Britain, an issue that one expert called "a potential treaty-buster" and "one of the most important obstacles to agreement."

With vigorous backing from London, Washington has strongly opposed the Soviets' demand that such sales end after completion of a current deal involving the Trident II, and pledged to give up the accord unless the Soviet demand is withdrawn.

Soviet officials say they understand that the Trident sales are part of an existing "pattern of cooperation" between the United States and Britain, and that past U.S.-Soviet arms accords have specifically allowed such cooperation to persist without limit.

But they say Soviet legislators will likely regard the continuation of such sales as a loophole enabling the United States to enlarge its strategic arsenal beyond treaty limits, in effect, even if the transferred weapons are to remain under British control.