The Soviet Union has serious doubts about Japan's desire to conclude a postwar peace treaty. So said a recent official Soviet statement presented to the Japanese ambassador in Moscow and later published by the Tass news agency. The stumbling block, as always, is Japan's insistence on the return of northern islands seized by Russian troops at the end of World War II.
The Japanese claim has been repeated at intervals over the past 30-odd years, but Prime Minister Zenko Suzuki seems to be showing more zeal over the issue than recent premiers.
Last September, Foreign Minister Masayoshi Ito laid the territorial problem before the United Nations General Assembly for the first time in eight years. And the Japanese government declared Feb. 7 "Northern Territories Day."
The argument is about the islands of Kunashiri, Etorofu, Shikotan, and Habomai, stretching from Japan's northernmost main island of Hokkaido to the Soviet territory of Sakhalin.
Japan bases its claim on a Feb. 7, 1885, Russo-Japanese treaty of commerce and navigation which set the border between the two countries at the strait north of Etorofu and recognized Japanese sovereignty over the four islands south of the line.
For many years now the Soviet position has been: "There is no territorial issue to be settled."
Japan's renewed claim on "Northern Territories Day" provoked a strong Kremlin outburst against Tokyo's "unrealistic and illegal demands."
Deput Foreign Minister Nikolai Firyubin called in Japan's ambassador in Moscow, Tokichiro Uomotu, to deliver a strongly worded letter that blamed the Japanese side for the absence of a World War II peace treaty.
The latest Soviet protest, as published by the Tass news agency, commented that "A legitimate question arises whether the Japanese side really wants a firm treaty base to be placed under our relations."
Repeating the Soviet proposal for a "good neighbors" treaty, Tass said: "It is this path . . . which can result in the establishment of a necessary treaty foundation in our relations."
Japanese officials echo some of the Soviet sentiments, saying that it is obviously Moscow which has no desire to put bilateral relations on a stronger foundation.
Japan certainly wants to conclude such a treaty but only after the territorial problem -- the last outstanding issue left over from the war -- is settled.
Tokyo has consistently rejected a Soviet counterproposal that, instead, the two countries merely sign a treaty of good neighborliness and cooperation.
Realistically, Japanese privately admit that there is little if any hope of getting the islands back.
But the issue remains one of more than symbolic importance in view of mounting evidence that the Soviets are fortifying the islands, building deepwater port facilities, air fields and military bases. Soviet warships and nuclear missile submarines now prowl along Japan's long coastline. Observers feel this is one of several factors prompting Suzuki to push the issue.
Another important consideration is that the issue gives Japan an opportunity to demonstrate its determination to show consistency in diplomacy and shake a long- standing reputation for opportunistic policy switches.
And the territorial issue is one of the few bargaining chips that Japan uniquely has with the Russians, and wielding it strongly establishes this country's image as an independent diplomatic enti ty in, say, Washington and Peking.