Russia proposed cutting nearly in half the number of nuclear warheads that would be allowed under a prospective START III treaty, a Russian official said today, as talks on the stalled arms control agreements resumed this week in Moscow.

President Clinton and Russian President Boris Yeltsin agreed in June to try to reanimate the long-dormant talks, including discussions on the unratified START II accord and the 1972 Anti-Ballistic Missile Treaty. The first round of discussions ended with renewed Russian warnings against modifying the ABM treaty.

The 1993 START II treaty called for reducing the levels of nuclear warheads to 3,500 to 3,000 on each side. But Russia's lower house of parliament, the State Duma, has resisted ratifying it.

At a meeting in Helsinki in 1997, Clinton and Yeltsin nevertheless set as a target for the next step, START III, a ceiling of 2,500 to 2,000 warheads for each side. However, a Russian official said that Moscow this week proposed slashing the maximum to 1,500 or fewer--a reduction that would reflect the reality of Russia's strategic forces, which are declining because of obsolescence and lack of money to build new systems. Many experts here think Russia's nuclear arsenal will decline to fewer than 1,000 warheads in the next decade.

Details of the latest Russian proposal were not provided, but it is likely to meet resistance in the Pentagon and among Republicans in Congress. Moreover, the United States has urged Russia to ratify START II before formal negotiations can begin on the follow-on treaty.

The ABM treaty also promises to incite a negotiating wrangle. The Clinton administration is headed toward a decision next year about building a missile defense system, and Yeltsin agreed to talk about possible changes in the ABM treaty at a summit meeting earlier this year. However, Russia has strongly resisted changes to the treaty, which limits the use of such systems by each country.

Meanwhile, some Republicans in Congress want to scrap the treaty altogether.

In a statement after this week's talks, the United States and Russia reaffirmed that the ABM treaty is "the cornerstone of strategic stability" and a Russian official openly warned against modifications.

Grigory Berdennikov, director of the Russian Foreign Ministry's security and disarmament department, told reporters: "We see no variants which would allow the United States to set up a national ABM system and still preserve the ABM treaty and strategic stability in the world."

He said any modifications would undermine the START treaties and expressed fear that "the arms race may spread into space."

If the United States deploys a missile defense system, he added, Russia "will be forced to raise the effectiveness of its strategic nuclear armed forces and carry out several other military and political steps to guarantee its national security under new strategic conditions."

He was not more specific, but cash-strapped Russia has barely been able to afford one missile modernization program in recent years.