Four weeks after signing a landmark treaty reducing conventional arms in Europe, the United States and the Soviet Union are embroiled in a dispute over the number of Soviet arms that must be destroyed under the accord, senior U.S. officials said in recent interviews.

The dispute arises from what officials of the Bush administration and some allied governments said is substantial Soviet underreporting of the number of tanks, armored infantry vehicles, artillery and aircraft required to be destroyed under the treaty, which the administration has not yet submitted to the Senate for ratification.

The Conventional Forces in Europe (CFE) Treaty, signed by leaders of 22 nations on Nov. 19, required an immediate declaration of all such arms deployed in a region stretching from the Atlantic Ocean east to the Ural Mountains, roughly 1,300 miles inside Soviet territory. Anything outside the region is not limited by the accord.

But U.S. officials said the Soviets declared at least 20,000 fewer weapons than Western officials believed they had, and also mislabeled some weapons, possibly to exempt them from destruction. They said the Soviets also appear to have transferred some undeclared arms outside the region after the treaty was signed, an action the treaty does not permit.

The member nations of the North Atlantic Treaty Organization and of the nearly defunct Warsaw Pact are allowed a total of 78,800 weapons each in the zones they occupy -- including 20,000 battle tanks, 30,000 personnel carriers and 20,000 artillery pieces. U.S. officials said there was no apparent discrepancy in the Soviet data on helicopters, none of which has to be destroyed.

Secretary of State James A. Baker III and chief U.S. negotiator R. James Woolsey raised the issue in Houston last week with Soviet Foreign Minister Eduard Shevardnadze, U.S. officials said. The Soviets promised to consider some of the U.S. complaints and respond promptly, but disagreed with others, the officials said.

U.S. officials have been reluctant to describe the Soviet actions as a treaty violation, noting that the accord allows signers 90 days -- until Feb. 17 -- to make "any necessary correction" to the data exchanged in an elaborate ceremony in Vienna last month. But several officials said they believed the discrepancies were not due to error but to deliberate misstatements by Soviet military officials.

They said the Soviet moves may be related to Moscow's desire to continue a massive transfer of older weapons -- which otherwise would be covered by the accord -- to military bases east of the Ural Mountains. Such Soviet shipments are aimed partly at avoiding the high costs of destroying tanks and other armored weapons, partly at preserving some extra military capability and partly at redressing the political embarrassment of having to destroy tens of thousands more weapons than NATO did, the U.S. officials said.

In some cases military commanders ordered to ship a certain number of weapons out of the region before the treaty was signed might have failed to meet the deadline and falsified reports to their superiors, one U.S. official suggested as a possible explanation for the data discrepancies. "This sort of thing has gone on for generations in the Soviet Union," the official said.

But several U.S. defense officials said they also feared that senior officers in the Soviet armed forces, some of whom have previously complained about the accord, might have decided against strict compliance and misled Soviet diplomats responsible for releasing the arms data.

The treaty provisions on weapon data were written largely by the United States and agreed to by other nations only a few days before the pact was signed. Several officials said the last-minute nature of the provisions might have caused confusion among the Soviets. Germany and several other European countries have already corrected what one U.S. official termed "gross mistakes" in their own data, with Soviet approval.

But U.S. officials said that during the consultations in Houston this week, Soviet officials challenged the U.S. view of restraints on land-based armaments, such as aircraft, attached to naval units. The application of the treaty to such weapons, which the United States does not have, was a highly contentious issue during the 18-month negotiations, "but one that we thought was settled," one official said.

He said that as a result, Washington was astonished when it appeared that the Soviet military had designated three regular Army divisions as units of naval infantry, which Moscow said are exempted from limitations.

Allied officials have also complained that the massive number of arms the Soviets have transferred from the affected region -- approaching 60,000 weapons, according to some estimates -- could violate the spirit of the CFE accord, if not its letter, even if the transfers occurred prior to signature, when they were permitted.

The Soviets have promised that most of the weapons transferred outside the region will be stored outside in harsh weather without routine maintenance, essentially allowing them to "rust away," one official said. But the Bush administration is trying to satisfy the concerns of U.S. allies by asking Moscow to provide assurances that a significant portion will be destroyed by readily observable techniques.

The administration last week notified key legislators and congressional aides that it probably will not submit the CFE accord for Senate approval until March, after the final Soviet data have been received. Several officials said they feared trouble during the Senate's deliberations if the Soviets do not acknowledge having larger weapons holdings on the signature date.