Mikhail S. Gorbachev arrives tonight for summit talks with President Bush that will focus on tough arms control and trade differences and search for common ground on the future of a unified Germany. The White House said Bush was in a mood of ``anticipation and confidence'' as Gorbachev wound up a brief visit to Canada and headed for his second summit with Bush and his first in Washington since he conferred with President Reagan in 1987. ``The president sees a new horizon in this meeting _ a horizon of opportunity,'' said presidential spokesman Marlin Fitzwater. ``After their discussions we should have a much better view of a new day in East-West relations.'' The Soviet president, in terms harsher than comments made the previous day, reaffirmed his country's opposition to a united Germany belonging to NATO. ``I haven't yet heard any alternative from the West,'' Gorbachev said after meeting with Canadian Prime Minister Brian Mulroney. ``It seems that it is just like an old record that seems to be playing the same note again and again. ... I would like us to find a new melody.'' Bush was spending his second consecutive day closeted with advisers over strategy for three days of summit talks starting Thursday. He also spoke by telephone this morning with West German Chancellor Helmut Kohl and Tuesday night with Canadian Prime Minister Brian Mulroney. Fitzwater said in a statement that Bush brings to the summit talk ``the understandings and insights of many allied leaders,'' including British Prime Minister Margaret Thatcher and French President Francois Mitterrand, with whom he met recently. Bush was not prepared to offer a position for future negotiations on the size of a unified German military _ a major concern of the Soviets _ Fitzwater said. The White House press secretary disputed news accounts suggesting Bush would offer assurances on limiting German forces to bolster Gorbachev's standing at home. On prospects for a trade agreement during the summit, Fitzwater said, ``I intentionally want to be vague.'' He added, ``I urge you not to rule out anything.'' ``This is an issue that really will depend on Gorbachev and Bush,'' he said. The Bush administration has held up the trade agreement to protest the Soviet Union's economic sanctions against Lithuania and Soviet failure to enact liberal emigration legislation. In a move to resolve disputed arms control issues, Col. Gen. Labronislav Omelichev, first deputy on the Soviet defense ministry's general staff, headed for Washington to enter talks on possible nuclear and conventional fores agreements for Bush and Gorbachev to announce. On the question of German troop levels, the United States still maintains such discussions should be held as part of future talks on reducing conventional forces in all of Europe, Fitzwater said. ``We are opposed to any proposal which would single out Germany for special limits,'' he said. However, Fitzwater said the summit would include ``discussions on the general question. We want to hear their concerns and their interests. We'll express our policy.'' ``This is not an issue which is linked in any way to German unity nor to the renunciation of four-power rights,'' Fitzwater said, referring to control of Germany's destiny by World War II victors Britain, France, the United States and the Soviet Union. ``President Bush will be exploring the subject with President Gorbachev from the standpoint of exploring mutually acceptable options and positions. Again, these issues are not going to be decided here,'' he said. However, an administration official who spoke on condition of anonymity said Bush hopes to nudge Gorbachev into accelerating the first round of conventional arms talks under way in Vienna, Austria, so a treaty can be completed by year's end. Bush was described as firmly opposed to a Soviet proposal that a united Germany be excluded from NATO's military structure while remaining within its political framework. Gorbachev was upbeat about the German issue as he spoke to reporters Tuesday outside Mulroney's residence in Ottawa. Gorbachev said he was confident that he and Bush will find a way to preserve the balance of power in Europe after East and West Germany are unified. Asked if he was optimistic about agreement on Germany and its membership in NATO, the Soviet leader replied: ``I am sure of that. And tell that to the American people.'' U.S. officials disclosed that Gorbachev would meet with South Korean President Roh Tae-woo in San Francisco after the Washington summit ends with a Bush-Gorbachev news conference on Sunday. The Soviet leader's plan to meet Roh was viewed as a further warming in relations between the two countries, which recently established ``consular departments'' in trade offices in each other's capitals. Before flying to Washington, Gorbachev acknowledged the emergence of a new domestic worry _ the election of political maverick Boris N. Yeltsin as president of the Russian republic _ as a major earthquake struck Eastern Europe. Gorbachev told reporters that ``everything is OK'' in the Soviet Union despite the quake that struck Romania this morning, killing eight people, injuring 260 and causing widespread damage. Tremors were felt in Moscow and Leningrad and a Soviet lawmaker said initial reports from the republic of Moldavia indicated there were an unspecified number of deaths. The Soviet leader said he saw no reason to break off his trip and return home. A major earthquake in Soviet Armenia in December 1988 forced Gorbachev to cut short a visit to the United Nations in New York, where he also met with President Reagan. In advance of the Soviet leader's early evening arrival, it was announced that Vice President Dan Quayle will meet Gorbachev briefly on Friday at the Soviet Embassy to discuss cooperation on space exploration. Arms control negotiators for the two countries, meanwhile, wrangled for more than two hours Tuesday over U.S. and Soviet conventional forces in Europe as well as their nuclear arsenals, including bombers and submarines. Meeting in secrecy at the State Department, they made some progress toward reductions in both areas. They agreed, for example, on definitions for such conventional weapons as tanks and armored personnel carriers, which will make it easier to verify that treaty terms are carried out, an official told The Associated Press on condition of anonymity. Although Secretary of State James A. Baker III's recent trip to Moscow led to agreement on sea and air-launched missiles, a handful of tough strategic weapons issues remained unsettled. Arms control issues still in dispute include whether to ban ballistic missiles with multiple warheads and the number of flight tests the Soviets could conduct of their heavy SS-18 missiles. The arsenal of such missiles is to be halved, from 308 to 154, but there is no agreement restricting improvement in the missiles that remain. Bush and Gorbachev still are expected to issue a joint declaration of progress toward a major reduction in nuclear arsenals, officials said, but they cautioned that long-range nuclear weapon issues still disputed may be excluded from that declaration. On the economic front, State Department spokeswoman Margaret D. Tutwiler said Tuesday that a new commercial air travel agreement has been initialed. Officials said it will be ready for signing at the summit.