TOKYO -- With Soviet President Mikhail S. Gorbachev due here Tuesday for a historic summit, no one on either side is guessing how far the trip will warm relations between two Far Eastern neighbors that still don't have a World War II peace treaty.
Mr. Gorbachev will make history simply by the arrival of his special plane Tuesday morning, for he will be the first top leader of his country -- imperial Russia or the Soviet Union -- to come here for a summit meeting.
To make sure that Mr. Gorbachev and Prime Minister Toshiki Kaifu will have something tangible to show after the four-decade wait since World War II for a Tokyo summit meeting, diplomats have prepared a stack of 14 documents for them to sign -- the usual stuff of improving relations, like cultural exchanges, trade exhibitions, environmental protection and long-deceased citizens buried in each others' countries.
But what Mr. Gorbachev most needs is massive sums of money to help refuel the flickering Soviet economy. Japanese newspapers have reported for a week that Tokyo is ready to provide a $28 billion package of easy credit and insurance for large-scale investment by Japanese companies.
What Mr. Kaifu says he'll insist on first is tangible progress toward a peace treaty, which to the Japanese means first and foremost the return of four tiny islands north of Hokkaido, seized by the Red Army on Stalin's orders as Japan's forces collapsed under U.S. pressure at the end of the war.
But both sides say nobody knows what Mr. Gorbachev may be willing to do about this central issue of the long-stunted relationship between the world's biggest country and the second-biggest economic power.
A Soviet advance party, led by V. N. Ignatenko, Mr. Gorbachev's chief spokesman, arrived here Friday and held a two-hour press conference at which members threw cold water on Japanese hopes for any early return of the islands.
"Most likely it will be years, but I hope it won't be decades," before the territorial issue can be resolved and a peace treaty can be signed, Konstantin O. Sarkisov, deputy director of the U.S.S.R. Institute for Oriental Research, said at that press conference.
The most that can be hoped, Mr. Sarkisov said, is that the Gorbachev trip "will start a process which must lead to the conclusion of a peace treaty."
Preparations have been replete with Japanese puzzlement at last-minute Soviet decision-making, not only on substantive issues but also on logistical details like what places Mr. Gorbachev wanted to visit and the addition early last week of an almost equally historic stop on Friday to see President Roh Tae Woo of South Korea, which has already signed up to give Moscow billions of dollars in economic help.
Despite endless uncertainties and scheduling glitches, the planning has also had the usual trappings of a late 20th-century summit, including the arrival last week of a bullet-proof limousine for the Soviet leader's travels about Japan.
By week's end, what had been decided about Mr. Gorbachev's three-day schedule here was redolent with the symbolism of emerging friendship, ranging from audiences with Emperor Akihito to a visit to the graves of 19th-century Soviet residents of Nagasaki, where he may also visit the Peace Park commemorating the world's second and last atomic bomb attack, by the U.S. Army Air Corps near the end of World War II.
Mr. Gorbachev will bring with him lists of the names of tens of thousands of Japanese captives who died in Soviet labor camps after the war, and on his way here he will stop to visit Japanese graves in the Soviet Far Eastern city of Khabarovsk.
At midweek, Nikolai Soloviev, the Soviet ambassador to China who was formerly stationed here and is still a key figure in Soviet Pacific affairs, said the heart of Mr. Gorbachev's visit will be, not a peace treaty, but a "new proposal for the security of Northeast Asia," centered on improving relations between Japan and his country.
Taizo Watanabe, the Japanese foreign ministry spokesman, said Friday that Japan is "not reluctant to talk with the Soviet Union about these matters," but that the central question is still a peace treaty.
The Soviet delegates argued Friday that Mr. Gorbachev's relentless domestic troubles mean now is no time for him to give away territory.
Japanese officials are just as adamant that the trip must produce "a breakthrough leading to dynamic development of our two countries' relations," as Mr. Watanabe put it Friday, making clear that this meant recognizable progress toward a peace treaty.
The Soviet leader has shown his ability to make difficult decisions in freeing Eastern Europe and liberalizing his own country, Mr. Watanabe said, so, "if there is any person who can bring about a dynamic change in our relationship, it must be Mr. Gorbachev."
As to any major Japanese funds for the Soviet economy without progress on the islands first, Mr. Watanabe said, that "is not something that we give priority to at this moment."
Japanese business executives have long coveted the coal, oil, timber and other resources the Soviets have so much trouble tapping in Siberia and the Far East, but they remain reluctant to trust the Soviet bureaucracy and economy with their money without major assurances from their own government in Tokyo.