WITH ample economic aid to offer as a lure, Japan welcomes the visit of a top Russian leader today in hopes of winning back four islands occupied by the Soviet Union since 1945.Ruslan Khasburatov, acting chairman of the Russian Supreme Soviet, will make a four-day trip to Tokyo, bringing with him a letter from Russian Republic President Boris Yeltsin. The letter and the visit, Japanese officials hope, could bring a breakthrough in the islands dispute similar to the granting of independence to the three Baltic states by Moscow last week. Japan has been the most reluctant among industrialized nations to offer aid to Moscow until it regains sovereignty over Etorofu, Shikotan, Kunashiri, and the Habomai group, what it calls the "Northern Territories." The islands are located just off the Japanese island of Hokkaido and are part of the Russian Republic. Many leaders in the Russian Republic "have their own free-thinking that the islands should be returned," says a top Japanese Foreign Ministry official. A resolution of the dispute, he adds, "will emerge from the new guiding forces in the Russian Republic." But Japanese leaders are confused over whether Mr. Yeltsin or Soviet leader Mikhail Gorbachev will have the most influence on the islands question following the shake-up after the failed August coup. Until now, Yeltsin has been more flexible than Mr. Gorbachev, suggesting the issue of the islands could be resolved in a few years. Gorbachev, by contrast, refused any compromise during a historic visit to Tokyo last April, although analysts speculated that he might have been under pressure from Communist conservatives. On Saturday, Yeltsin was quoted by Interfax, the independent Soviet news agency, as saying the islands were not a subject for bargaining. This stance is consistent with Moscow's previous insistence that the islands will not be traded for money. Japanese officials agree that aid and investment will not be granted directly in return for the islands. Unsure of who holds the upper hand in Moscow, Japan did not officially recognize the Baltics until after the interim state council run by both Gorbachev and Yeltsin granted them independence Sept. 6. One sign of a power shift in Moscow was an interview given by the new Soviet Foreign Minister Boris Pankin to Japan's largest newspaper, Yomiuri. Mr. Pankin said each republic can solve bilateral issues with neighboring nations under the new and tentative federal system. "In principle, I welcome the Russian leadership's active approach to resolving the issues with Japan," Pankin said Friday. The foreign minister also hinted of a new attitude toward Japan after the removal of many conservative leaders. The abortive coup, Pankin said, has removed "elements disturbing improvement of Japan-Soviet relations." Japan has also linked any future financial aid to moves toward democracy and a market economy in the Soviet Union, a stance in line with its summit partners. Now that such moves appear to be underway with the demise of Soviet communism, Japan is in a dilemma over how much aid to give. "I think Japan should not neglect any effort of supporting [the changes] and making effective assistance," said the Japanese Foreign Ministry official, adding that he was speaking for himself. Until now, Japan has only offered technical economic advice and $100 million in humanitarian food aid to Moscow. Even more of a dilemma for Japan is whether a real democracy might emerge in the Russian Republic - a move strongly advocated by Japan - but with a Russian majority opposing a return of the islands. "The resolution of the North Territories issues is based on justice," explains the Foreign Ministry official. "The more that the Russian people become democratic and judge things on their own thinking, then the righteousness of the issue will become more apparent."