President Bush and Soviet President Mikhail Gorbachev yesterday announced their long-promised agreement on basic provisions of a landmark treaty slashing U.S. and Soviet strategic nuclear weapons and, in an unexpected move, signed a commercial accord to facilitate trade between the two countries.

The agreements on these and other questions were announced in the White House East Room following a day of suspense and intense last-minute negotiations between Secretary of State James A. Baker III and Soviet Foreign Minister Eduard Shevardnadze on the details of the arms declaration and the surprise trade pact.

"The world has waited long enough. The Cold War must end," Bush declared as he and Gorbachev prepared to sign seven U.S.-Soviet accords. The Soviet leader, in reply, cited President Franklin D. Roosevelt's "four freedoms" declaration of 1941 and said that, "while liberating the world from fear, we are making steps toward a new world."

To leaders of Congress in public and to Bush in private, Gorbachev made fervent pleas for the trade pact as a political gesture of great importance to him at home. Experts said its symbolic impact is likely to far exceed its practical significance, because it must be approved by a still-skeptical Congress and will have little effect in the absence of a more controversial measure granting the Soviet Union most favored nation (MFN) trade status, which still has not been authorized by the administration.

Bush told Gorbachev he will not send the trade pact to Capitol Hill until the Supreme Soviet passes a law codifying the Soviet Union's more liberal emigration policies. An official said Bush told Gorbachev he could not understand why this had not been done already, and Gorbachev responded that he would redouble his effort to obtain passage of the act, which was recently removed without explanation from the agenda of the Supreme Soviet.

Bush previously had expressed reluctance to move ahead with the trade accord while the Soviet Union continues its economic embargo of breakaway Lithuania. U.S. officials said "a very heavy debate inside the administration" over the Soviet trade issue had been tipped in Gorbachev's favor by the Soviet leader's persistent and extensive personal lobbying.

Gorbachev, starting with the first meeting in the Oval Office Thursday morning, repeatedly raised the trade pact with Bush, an administration official said last night. The initial discussion was "a hard first pitch . . . a very strong plea" by Gorbachev, the official said, followed by further pleas to Bush during the White House state dinner Thursday night and in another Oval Office meeting yesterday. Bush decided in mid-afternoon to sign the trade agreement, according to this account, though he informed Gorbachev flatly that it would be "extraordinarily difficult" to obtain congressional approval without a resolution of the Lithuanian issue.

Even after Gorbachev's impassioned plea to lawmakers for the trade pact during an unusually direct and candid breakfast presentation, congressional leaders expressed skepticism in the absence of an accord between the Kremlin and Lithuania. The Senate asked Bush by a 73-to-24 vote May 1 not to send it a trade agreement for approval while the Moscow-Lithuania crisis persists.

Bush and Gorbachev also signed a new five-year agreement on Soviet purchases of American grain. There were reports that Gorbachev had balked at signing the grain pact, of great interest to U.S. farmers, unless Bush signed the trade pact, but administration sources said Gorbachev had made no direct threat.

Speaking to reporters last night, Baker refused to answer questions about whether the grain agreement with the Soviet Union had become a last-minute bargaining chip in the talks over the trade deal.

The two leaders also signed an accord pledging to slash their stockpiles of chemical weapons and to halt immediately further production of poison gas. Additional accords on nuclear testing, peaceful uses of atomic energy and university student exchanges were signed by Bush and Gorbachev, while senior aides affixed signatures to still other U.S.-Soviet pacts.

The joint statement on approval of the main points of the Strategic Arms Reduction Treaty (START), which had been announced as a central objective for the current summit when the two leaders met six months ago at Malta, was the subject of three hours of last-minute Baker-Shevardnadze bargaining that delayed the White House signing ceremony by more than an hour.

Bush and Gorbachev also agreed on a statement of objectives for the next round of strategic arms talks that commits both countries to pursue reductions in missiles carrying multiple nuclear warheads. They also agreed to press for an early agreement on weapons in space and the Anti-Ballistic Missile (ABM) Treaty, a reference to the U.S. Strategic Defense Initiative that the Soviets have long sought to block.

The 11th-hour negotiations apparently were unsuccessful in reaching agreement on some of the complicated issues of START treaty detail still outstanding. Baker said last night that the two sides had resolved questions of sub-limits on mobile missiles, but were unable to resolve differences over the Soviet Union's Backfire bomber, limits to testing of Soviet heavy missiles and the question of "non-circumvention" of the pact.

A lengthy joint statement on the START agreement listed provisions that would cut some categories of Soviet nuclear weaponry by 50 percent and other parts of the U.S. and Soviet arsenals by about 30 percent. Critics, however, maintained that in view of continuing modernization of the arsenals and special provisions for some programs, the actual cutbacks from current levels will be marginal at best.

Bush and Gorbachev reconfirmed their commitment to sign the START treaty by the end of this year.

Bush and Gorbachev also issued a statement pledging to accelerate work toward completion this year of a 23-nation treaty slashing U.S. and Soviet land armies and other non-nuclear forces in Europe. Baker said "this summit has helped somewhat to narrow the gaps between the two sides" on conventional forces but that "serious, substantive differences remain."

If both the START and conventional forces treaties are signed this year, Gorbachev noted last night, this will provide the occasions for two more meetings with Bush in 1990.

The White House signing ceremony was the high point of a day of extraordinary international politics and diplomacy, mixed with vivid images of the Soviet Union's first couple. Gorbachev's sometimes gripping appeal to U.S. congressional leaders, which was carried live on Cable News Network to the surprise of the legislators and perhaps unknown to the Soviet leader, was followed by two unscheduled Gorbachev stops on downtown Washington streets, where he was cheered by crowds.

In the afternoon, Gorbachev received five humanitarian awards from varied U.S. groups at the Soviet Embassy, and said the recognition is "a great incentive to me in what I'm doing."

Raisa Gorbachev, meanwhile, joined Barbara Bush at commencement ceremonies at Wellesley College. This was barely over before an announcement about 2:30 p.m. that Baker and Shevardnadze had begun unexpected 11th-hour negotiations over provisions of the START treaty, which imparted the air of a cliffhanger finish to the long-planned celebration of U.S. and Soviet accords in the East Room.

The two leaders ended their day at a dinner hosted by Gorbachev at the Soviet Embassy. The Soviet president, in his toast, praised the late Andrei Sakharov, whom Bush had quoted approvingly in the arrival ceremony for Gorbachev Thursday, as a man ahead of his time. "Sakharov had the courage of his convictions to uphold to the end that force could no longer play a role in relations among states," said Gorbachev of the famous physicist who was exiled by the Kremlin in 1980 to a provincial city under house arrest until Gorbachev brought him back to Moscow in December 1986.

The completion of the START declaration and signing of the trade and grain agreements cleared away nearly all of the pressing business to be discussed at the summit. Baker said the two leaders will discuss regional issues, including Afghanistan, the state of perestroika and U.S.-Soviet economic relations today at the presidential retreat at Camp David.

Despite optimistic statements from Gorbachev and Bush Thursday about discussions on Germany, administration officials said that little progress had been made toward a meeting of the minds and that it was evident it will take a much longer time to bridge the wide gap between the two sides.

The "in-depth" discussions of emerging ideas on this subject that had been promised by the two sides probably will not be held at this summit but reserved for other Baker-Shevardnadze meetings next week and at future times, White House press secretary Marlin Fitzwater said.

Bush's decisions to sign the trade pact without major progress on Lithuania could generate controversy. The administration last night sought to minimize any relationship between the two subjects.

Baker, at a news conference, said "there has been no formal linkage by anybody in this administration that I am aware of" between U.S. concerns over Lithuania and the commercial trade agreement. "I have not seen any statements formally linking the two."

When reporters reminded Baker that Bush had said last week that the political climate in this country would make it "extraordinarily difficult" for Congress to approve most favored nation trade status for the Soviet Union while the Lithuania crackdown continued, Baker urged reporters to ask the president again at his Sunday news conference. On May 24, Bush said: "Let's hope there's some progress on the Lithuanian question, because I think many feel there's a direct linkage there {with granting the Soviets MFN}, and I must say it concerns me."