Bush and Gorbachev OK Arms Pact, Plan Summit July 30-31 : Diplomacy: The treaty will require massive cuts in long-range nuclear weapons. Group of 7 also reveals a support plan for the Soviets and recommits itself to freer trade.

President Bush and Soviet President Mikhail S. Gorbachev, in a historic decision that ended nine years of tortuous negotiations, agreed Wednesday on a Strategic Arms Reduction Treaty that will require both sides to slash their arsenals of long-range nuclear weapons.

Arms negotiators in Geneva plan to complete the wording of the highly complex START treaty in time for Bush and Gorbachev to sign it at a Moscow summit they agreed to hold July 30-31.

The treaty will require both countries to reduce their massive arsenals of long-range nuclear weapons by about a third overall and the most dangerous category--ballistic missile warheads--by a half.

Both leaders declared that Wednesday’s action, which would clear the way for the first verified reduction of the strategic arsenals of both countries, was reached through mutual compromise and represents a common victory.

In the final analysis, however, the Soviets made a political decision to break the deadlock on the last remaining issue dividing the two sides by agreeing with the U.S. position on how to resolve questions dealing with missile “throw-weight”--a measure of the size of a missile and the payload it can deliver.

Bush proclaimed U.S. defense experts “so enthusiastic” about the treaty that, when it comes up for ratification, it should “sail through the Senate.”

The strategic arms accord was the most dramatic in a string of developments as the leaders of the seven largest industrial democracies met first among themselves and then with Gorbachev. In addition, the seven leaders:

* Responded to Gorbachev’s plea for economic support with a six-point plan including technical support and associate membership in the International Monetary Fund--but no massive financial assistance.

* Recommitted themselves to liberalizing the rules governing international trade but failed to settle any of the disputes that have blocked agreement in the five-year trade talks.

* Pledged to work toward global environmental improvements but did not set targets to meet such threats as global warming.

The START agreement, considered one of the most technically complex accords ever negotiated, sets an absolute limit of 1,600 missiles and heavy bombers for each nation and lays down rules governing warheads, mobile missiles and large-capacity intercontinental ballistic missiles, air-launched and sea-launched cruise missiles and bombers.

The treaty also contains elaborate provisions for verifying compliance, including on-site inspection of each side’s arsenal before reductions begin as well as short-notice inspections and even continuous monitoring of hardware and facilities considered especially sensitive.

The agreement, once ratified by both sides, is to take effect over a seven-year period and is to remain in force for 15 years with provisions for extending it further into the future.

The final breakthrough on the arms reduction treaty came when Soviet Foreign Minister Alexander A. Bessmertnykh asked to meet with Secretary of State James A. Baker III and notified him during a 15-minute meeting Wednesday morning that the Soviets were ready to approve the latest version, including a compromise on the throw-weight issue.

Throw-weight is usually defined as the weight of a missile’s payload, including the warheads and the so-called bus that houses them. But U.S. and Soviet negotiators have long disagreed on a precise definition. The last issue blocking the treaty was the question of how much throw-weight would have to be added to an existing missile for it to be considered a new type of missile.

Neither side would disclose the details of the throw-weight compromise, and the official negotiating positions of both sides have always been secret. U.S. officials turned aside questions as to how the compromise was reached, with National Security Adviser Brent Scowcroft saying: “What we don’t want to get into is, in the end game, who won, who lost, and so on. . . . You know, arms control is not a zero-sum game. It’s trying to arrive at something that satisfies the needs and national interests of both sides.”

At 1 p.m. London time, 65 minutes after the meeting of the American and Soviet foreign ministers, Bush and Gorbachev officially agreed on the pact during a brief meeting in a living room of stately Winfield House, the U.S. ambassador’s residence in London’s Regent’s Park.

Bush, looking tired and drawn from his hectic pace in Europe, opened a brief joint press conference with Gorbachev at Winfield House with a tame statement that they had made progress on the arms and economic fronts. He left it to the Soviet leader to make the official announcement that they had agreed on a START treaty.

” . . . In view of the fact that we were told that all of the issues are solved on the START treaty, we, with the President of the United States, have agreed to finalize everything in Geneva, and we will give commensurate instructions so that we could then sign that treaty,” Gorbachev said.

Until the end, U.S. officials had repeatedly stressed the importance of the last issue dividing the two countries. As recently as Wednesday morning, less than six hours before the agreement was reached, Scowcroft described it as “an extremely technical but very important issue.”

In a television interview, Scowcroft, hinting that the Soviets would have to agree to the U.S. position if there was to be an agreement, said that “a breakthrough is going to take a political decision, I think, rather than an expert decision.”

Later Wednesday, several hours after his press conference with Gorbachev, Bush met again with reporters in the garden at Winfield House and once again insisted that there were “no winners and losers” in the final agreement on START.

But he confirmed that in reaching the agreement, the Soviets “felt they had met the criteria spelled out by Baker and the defense experts.”

Bush said he had been “marginally involved” in the treaty negotiations during the past nine years. He gave credit to former President Ronald Reagan for wrestling with the arms control issue during “turbulent changes in U.S.-Soviet relations.”

At their joint press conference, held in a small drawing room packed with about 100 American and Soviet journalists, a smiling Gorbachev said:

“Once again, I’ve invited the President to come to the Soviet Union at the very end of July. . . . The Soviet people, all of us, will be ready to give our hospitality to the President of the United States and, I also hope, to Mrs. Bush, and to all those who will accompany him.”

Bush, accepting the invitation, said he looks forward to working with the leaders of the six other industrialized democracies in helping Gorbachev with the “big job” of converting the Soviets’ centrally planned economy into one driven by market forces.

“But thank you, Mikhail, for your invitation; and before you change your mind,” the President said as the room rocked with laughter, “we accept with pleasure.”

Although the President appeared to be in a jovial mood, he reacted with some heat when Helen Thomas, veteran White House correspondent for United Press International, tried to pin him down as to which side capitulated to reach the final accord.

“Helen always asks the questions where there has to be a winner or a loser or somebody continuing to fight. . . ,” Bush retorted. “There was compromise on all sides, and it’s in the best interest of the United States, and I hope that the Soviet people feel it’s in the best interest of the Soviet people.”

Gorbachev, concurring, said: “We will not be able to succeed either today or tomorrow in building new international relations . . . if we try to win. We have to move reciprocally toward each other in the interest of all mankind. . . . So it’s our common victory.”

Although the press conference had been scheduled for half an hour, Gorbachev called a halt after only eight minutes, saying, “Thank you, ladies and gentlemen.”

A bemused President Bush asked, “Are we finished?” And a reporter quickly asked Gorbachev whether the political support and technical assistance the summit nations were extending to aid the ailing Soviet economy was enough, “or are you looking for a bundle of cash here?”

The Soviet leader, after a loud but good-natured grunt, said, “Well, that’s my general answer.”

Immediately after the press conference, Baker told reporters that whether the wording of the treaty would be completed in time for Bush and Gorbachev to sign it at the Moscow summit was “still up in the air.”

But minutes later, a senior Administration official rushed out of Winfield House to assure departing reporters that “we have a START agreement that will be ready for signature at the summit in Moscow. And what the negotiators in Geneva will be working on is the treaty language that implements the agreement that’s been reached here today.”

Earlier that day, after Bessmertnykh asked to meet with Baker, Bush huddled with his secretary of state and other senior advisers for a final review of the U.S. position.

Fifteen minutes into his session with Bessmertnykh, Baker notified Bush and Scowcroft that an agreement had been reached, pending a final discussion between Bush and Gorbachev. Bush and Scowcroft then met briefly in the hallway with Bessmertnykh, who confirmed the agreement.

At noon, Gorbachev arrived for a luncheon session with Bush. Despite the historic nature of the agreement, the two leaders did not discuss the treaty but instead held a general discussion about the Soviet economy and Gorbachev’s plans for reforms.

“There was a lot of philosophy in it,” said a senior Administration official. “Questions like President Gorbachev asking President Bush what he would like to see for the Soviet Union, where he thinks they should be going. President Bush talked in terms of democracy, elections, private markets, open economy, participation in world affairs, etc. President Gorbachev talked about his dreams for the country and what he was trying to do.”

Immediately after the luncheon, the two leaders walked into a living room at the back of the house and, during a brief discussion, shook hands on the historic deal. Then they strode into the drawing room to make the announcement.