YASUHIRO NAKASONE, THE FIRST JAPANESE PRIME MINISTER TO MAKE AN OFFICIAL VISIT TO EASTERN EUROPE, LEFT TOKYO ON JANUARY 10 FOR A WEEK-LONG TOUR OF FINLAND, EAST GERMANY, YUGOSLAVIA AND POLAND. POLITICAL ANALYSTS BELIEVE NAKASONE IS HOPING THE TOUR WILL LEAD TO AN IMPROVEMENT IN RELATIONS BETWEEN JAPAN AND THE SOVIET UNION, AFTER SOVIET LEADER MIKHAIL GORBACHEV TURNED DOWN AN INVITATION TO VISIT JAPAN. BUT GORBACHEV HAS APPARENTLY NOT RULED OUT A FUTURE TRIP TO JAPAN, IF NAKASONE'S EASTERN EUROPEAN TOUR IS A SUCCESS. THE TRIP TO JAPAN, IF NAKASONE'S EASTERN EUROPEAN TOUR IS A SUCCESS. THE ONLY OTHER JAPANESE PRIME MINISTER TO VISIT EASTERN EUROPE WAS THE LATE MASAYOSHI OHIRO WHO MADE AN UNOFFICIAL TRIP TO YUGOSLAVIA IN 1980, FOR THE FUNERAL OF YUGOSLAV PRESIDENT TITO.