President Reagan is "strongly leaning" toward accepting a "build-down" nuclear arms reduction proposal under which the United States and the Soviet Union would destroy two nuclear warheads for each additional warhead deployed in the future, well-placed administration officials said yesterday.

They said the president has accepted the concept of build-down and of incorporating it in revised U.S. proposals to be submitted at the Strategic Arms Reduction Talks (START) in Geneva.

But they emphasized serious unresolved questions about the technical language of the proposal intended for submission when the deadlocked START talks resume June 8. One official acknowledged that endorsement of the build-down idea, as urged on the president in a letter April 29 by Sens. William S. Cohen (R-Maine), Sam Nunn (D-Ga.) and Charles H. Percy (R-Ill.), may be a condition for Senate approval of the MX nuclear missile.

However, the official cautioned that verification, already a concern of Reagan, would become even more important if build-down is adopted because the United States would have to be certain that the Soviets actually destroy old weapons.

The officials emphasized that no formal decision was reached yesterday at a National Security Council meeting on build-down or on other proposed changes in U.S. positions at the Geneva talks. The present U.S. proposal calls for both sides to reduce their forces to 850 missiles each.

"There is a general consensus to depart from 850 but whether to raise it or do away with it is up to the president, and both arguments have merit," one official said.

The administration appeared to be moving yesterday toward doing away with the missile limit and relying instead on the number of warheads as the main measurement of the nuclear arsenals of the two superpowers.

Speaking of prospective changes in the U.S. START position, White House spokesman Larry Speakes said, "It's likely that these modifications will be in the direction of the Scowcroft commission call for further emphasis on warheads as a unit of account."

The President's Commission on Strategic Forces, headed by former Air Force Gen. Brent Scowcroft, called for deploying 100 MX missiles in existing Minuteman silos and developing a smaller, single-warhead missile that would provide a less-tempting target. The commission also proposed counting warheads rather than launchers in arms control negotiations.

Reagan mentioned the START proposal only briefly yesterday at a White House meeting with a group of House members, most of whom support the MX.

The president said he considered the Scowcroft commission recommendations a single, interrelated package. He did not say and was not asked whether he had agreed with a recommendation contained in the Senate letter and another from three moderate House Democrats urging creation of a presidential advisory commission on arms control.

This proposal has encountered serious opposition from national security officials who say the panel would duplicate ones in existence. But officials said yesterday that Reagan is likely to agree to it as a way of obtaining additional bipartisan backing for the MX and the smaller missile.

During the last two weeks, in public and private discussions, the president and his senior advisers have stressed "bipartisanship" as a key to winning congressional approval of the MX after rejection of two previous Reagan proposals to deploy the intercontinental ballistic missile.

In this effort to win the backing of on-the-fence members of Congress, the build-down idea has become a key despite reservations about it by some administration arms specialists.

After testifying in favor of the MX yesterday before a Senate appropriations subcommittee, Richard Perle, assistant secretary of defense for international security policy, told reporters that the administration is "trying to find a way to extract what is President Considering Revised Arms Proposal By Lou Cannon Washington Post Staff Writer

President Reagan is "strongly leaning" toward accepting a "build-down" nuclear arms reduction proposal under which the United States and the Soviet Union would destroy two nuclear warheads for each additional warhead deployed in the future, well-placed administration officials said yesterday.

They said the president has accepted the concept of build-down and of incorporating it in revised U.S. proposals to be submitted at the Strategic Arms Reduction Talks (START) in Geneva.

But they emphasized serious unresolved questions about the technical language of the proposal intended for submission when the deadlocked START talks resume June 8. One official acknowledged that endorsement of the build-down idea, as urged on the president in a letter April 29 by Sens. William S. Cohen (R-Maine), Sam Nunn (D-Ga.) and Charles H. Percy (R-Ill.), may be a condition for Senate approval of the MX nuclear missile.

However, the official cautioned that verification, already a concern of Reagan, would become even more important if build-down is adopted because the United States would have to be certain that the Soviets actually destroy old weapons.

The officials emphasized that no formal decision was reached yesterday at a National Security Council meeting on build-down or on other proposed changes in U.S. positions at the Geneva talks. The present U.S. proposal calls for both sides to reduce their forces to 850 missiles each.

"There is a general consensus to depart from 850 but whether to raise it or do away with it is up to the president, and both arguments have merit," one official said.

The administration appeared to be moving yesterday toward doing away with the missile limit and relying instead on the number of warheads as the main measurement of the nuclear arsenals of the two superpowers.

Speaking of prospective changes in the U.S. START position, White House spokesman Larry Speakes said, "It's likely that these modifications will be in the direction of the Scowcroft commission call for further emphasis on warheads as a unit of account."

The President's Commission on Strategic Forces, headed by former Air Force Gen. Brent Scowcroft, called for deploying 100 MX missiles in existing Minuteman silos and developing a smaller, single-warhead missile that would provide a less-tempting target. The commission also proposed counting warheads rather than launchers in arms control negotiations.

Reagan mentioned the START proposal only briefly yesterday at a White House meeting with a group of House members, most of whom support the MX.

The president said he considered the Scowcroft commission recommendations a single, interrelated package. He did not say and was not asked whether he had agreed with a recommendation contained in the Senate letter and another from three moderate House Democrats urging creation of a presidential advisory commission on arms control.

This proposal has encountered serious opposition from national security officials who say the panel would duplicate ones in existence. But officials said yesterday that Reagan is likely to agree to it as a way of obtaining additional bipartisan backing for the MX and the smaller missile.

During the last two weeks, in public and private discussions, the president and his senior advisers have stressed "bipartisanship" as a key to winning congressional approval of the MX after rejection of two previous Reagan proposals to deploy the intercontinental ballistic missile.

In this effort to win the backing of on-the-fence members of Congress, the build-down idea has become a key despite reservations about it by some administration arms specialists.

After testifying in favor of the MX yesterday before a Senate appropriations subcommittee, Richard Perle, assistant secretary of defense for international security policy, told reporters that the administration is "trying to find a way to extract what is positive from that build-down proposal without binding our modernization program beyond what is reasonable."

Rep. Samuel S. Stratton (D-N.Y.) emerged from the White House meeting with Reagan to say:

"You're going to have build-down because you're going to put them MXs in Minuteman silos . . . . You're going to have to put the 100 MXs in 1,000 holes, and you're going to have in effect the same kind of arrangement that was proposed in the Carter administration, the multiple basing so that you have deception. The Russians won't know which Minuteman holes they're in."

The White House yesterday released a transcript of what it called "the president's responses" to questions submitted by the German magazine Bunte. An official said the replies were prepared in the White House and approved by Reagan.

Responding to a question about whether it would be possible to limit a nuclear war to Europe, the president emphasized that U.S. policy is to settle differences peacefully.

"We and our allies will not use any of our weapons, except in response to aggression," Reagan said. "I don't believe a limited nuclear war is possible."

Staff writers Michael Getler and David Hoffman contributed to this report. positive from that build-down proposal without binding our modernization program beyond what is reasonable."

Rep. Samuel S. Stratton (D-N.Y.) emerged from the White House meeting with Reagan to say:

"You're going to have build-down because you're going to put them MXs in Minuteman silos . . . . You're going to have to put the 100 MXs in 1,000 holes, and you're going to have in effect the same kind of arrangement that was proposed in the Carter administration, the multiple basing so that you have deception. The Russians won't know which Minuteman holes they're in."

The White House yesterday released a transcript of what it called "the president's responses" to questions submitted by the German magazine Bunte. An official said the replies were prepared in the White House and approved by Reagan.

Responding to a question about whether it would be possible to limit a nuclear war to Europe, the president emphasized that U.S. policy is to settle differences peacefully.

"We and our allies will not use any of our weapons, except in response to aggression," Reagan said. "I don't believe a limited nuclear war is possible."