Bush, Advisers Clear Up U.S. Position on START Pact : Arms control: Baker will present the new American position today. The goal is to complete the treaty in time for the summit in Moscow.

The Bush Administration has resolved internal conflicts holding up the U.S.-Soviet Strategic Arms Reduction Treaty (START) and will seek to complete the agreement in time to hold a superpower summit in Moscow late this month or in early July, U.S. officials said Thursday.

Secretary of State James A. Baker III, in Copenhagen for a North Atlantic Treaty Organization meeting, said he will outline the new U.S. position on START at a meeting with Soviet Foreign Minister Alexander A. Bessmertnykh in Geneva today in a effort to resolve remaining issues.

President Bush, returning to Washington from a speech in Atlanta, told reporters aboard Air Force One that he is eager to meet with Soviet President Mikhail S. Gorbachev again but indicated that setting a summit date will depend on the Soviet response to the new U.S. offer on START.

“It’s a two-way street here,” Bush said of the arms talks. But he added: “Both sides are dealing in very good faith at this point, and both sides want to have a summit, and both sides obviously want to have a strategic arms agreement.

“That has not always been the case necessarily,” the President added in what appeared to be a rare public admission of a longstanding split within his Administration, as well as between the United States and the Soviet Union, on the last outstanding obstacle to START.

The treaty, now 98% complete, would reduce the long-range nuclear weapons of both sides by about one-third overall and cut the most dangerous types of weapons--the warheads on ballistic missiles--by about one-half.

The landmark treaty, a 500-page document that Soviet arms expert Alexei G. Arbatov called “the most far-reaching and complex international law document in history,” has been held up by a seemingly ludicrous dispute: not how many warheads can be put on a missile but how many can be taken off.

The issue of “downloading”--removing warheads from existing missiles--is considered critical because it involves a potential loophole that could enable one country to quickly rearm its missiles in violation of the treaty limits. The matter created an unusual rift within the Administration, with National Security Adviser Brent Scowcroft and Baker taking opposite sides on the issue, according to Administration officials.

Downloading would make it easier and cheaper for the United States and the Soviet Union to comply with START provisions that would impose on each side a limit of 4,900 ballistic missile warheads--roughly half their present arsenals. The Pentagon, for example, has proposed to download its Minuteman III missile from three warheads to either one or two warheads each.

The alternative to downloading would be to design and develop totally new systems to carry fewer warheads than present missiles.

Experts on both sides applaud the idea of equipping missiles with fewer warheads because doing so would reduce the danger of surprise attacks. Distributing warheads more widely, among a larger number of missiles, makes an attack more complicated and its outcome more dubious, and thus less likely to occur. Previous U.S.-Soviet summits have declared that this concept should be pursued in talks following completion of a strategic arms treaty.

The catch, however, is that downloading would create “empty spaces”--as many as 2,000--on each country’s existing missiles. The spaces could be refilled quickly, providing one side a significant advantage of as many as 40% more warheads than its adversary.

The split within the Administration over the downloading issue had prevented U.S. negotiators from seriously seeking its resolution with the Soviets until now, U.S. officials said.

Scowcroft, an arms control expert, has been more worried than Baker about the long-term military consequences of empty spaces on Soviet missiles. He recognizes the advantages of downloading but fears the “break-out potential” it would involve, one Administration official said.

Baker, for his part, has been “more flexible, looking at the broader political perspective” of taking another step forward in U.S.-Soviet relations, the official said.

“A compromise involving a limited amount of downloading” was reached following a Wednesday morning meeting among Bush, Scowcroft, Baker, Defense Secretary Dick Cheney and Gen. Colin L. Powell, chairman of the Joint Chiefs of Staff, an official said.

A new U.S. position on this issue, as well as on two other outstanding START matters, was formally approved by the National Security Council on Thursday.

The precise nature of the compromise was unclear. But it could set as many as three kinds of limits on downloading: the total number of empty spaces that could be created, the maximum number of such spaces on each missile, and a limit on the different types of missiles that could be downloaded.

Earlier, the Pentagon and State Department proposed that each country could download a total of about 1,000 warheads on two types of missiles--one land-based and one submarine-based. Moscow wants at least 2,000 empty spaces altogether, but its position is complicated by the fact that it previously downloaded one type of missile that it does not want counted against any new limit.

A related issue involves defining what constitutes a new missile as opposed to an old one. While seemingly arcane, officials believe that the matter must be resolved to prevent downloading by a different name. Moscow wants the definition to be loose, to allow old missiles to undergo minimal modifications and then be categorized as new missiles loaded with fewer warheads. But Washington insists that a new missile must be significantly different in several respects.

A final outstanding problem involves how to ensure that in-flight testing data is not encoded or otherwise denied to the other side.

Times staff writers Doyle McManus, in Copenhagen, and James Gerstenzang, in Washington, contributed to this story.