In October 1973, Prime Minister Kakuei Tanaka pressed Soviet leader Leonid Brezhnev into admitting during a bilateral summit that a dispute over Japan's claim to the Northern Territories constituted one of the "problems" during work to draft a joint communique.

The scene was described in detail in secret proceedings of the meeting discovered recently.

Tanaka was visiting the Soviet Union at the time. But Brezhnev, general secretary of the Soviet Communist Party, refused to discuss the territorial dispute.

In the end, both leaders confirmed verbally that Tokyo and Moscow should solve the issue of sovereignty of the four islands off the eastern coast of Hokkaido when concluding a peace treaty to formally end hostilities emanating from World War II.

Nearly 50 years later, Japan still clings to the basic stance enunciated by Tanaka in its talks with Russia over the territorial issue.

The uncovered document titled "records of Prime Minister Tanaka's Soviet visit and talks," and crafted by the Foreign Ministry's first Eastern Europe division, which dealt with the Soviet Union, is labeled, "top secret, indefinite period."

It was found in an archive of documents kept by former Prime Minister Takeo Miki, who was deputy prime minister at the time, and donated to Meiji University, his alma mater, after his death.

Full proceedings of the 1973 Japan-Soviet summit had never been brought to light until now.

According to the document, Brezhnev proposed, during the third of the four rounds of the summit held while Tanaka was in the Soviet Union, that both countries work out "principles on peace and cooperation," apart from a peace treaty, which still has not been concluded because of the territorial standoff.

Tanaka rejected the proposal out of a fear the territorial issue could be shelved.

Tanaka argued he would not agree to release a post-summit communique unless the four islands of Habomai, Shikotan, Kunashiri and Etorofu were to be expressly included in the topics of talks for concluding a peace treaty.

Brezhnev retorted: "That's impossible. Continuation of the talks need not be included in the communique if that's unacceptable for you. That's Japan's problem."

During the last round of the talks, both leaders had a tit-for-tat over what the word "problems" was intended to mean in a passage of the Soviet draft of a joint communique that read, "solving the problems that have remained pending since World War II and concluding a peace treaty."

Tanaka told Brezhnev, "I want you to remember that the four islands are part of those ('problems')."

Brezhnev replied, "Ya znayu (I know)."

Tanaka pressed him again by saying, "I want you to confirm once more that the four islands are part of the 'problems.'"

Brezhnev nodded and said, "Da (Yes)."

Both parties settled on adopting the Soviet draft for the joint communique.

"The phrase 'Ya znayu' was not firm enough," Hirokazu Arai, who attended the summit in the capacity of then head of the first Eastern Europe division, told The Asahi Shimbun in an interview. "So I jotted down in a note, 'Ask once more, please.' I handed over to the prime minister via Foreign Minister Masayoshi Ohira (a later prime minister), who was sitting next to me."

The policy to resolve the issue of the four islands in concluding a peace treaty, which was confirmed verbally during the meeting, was stipulated expressly in the 1993 Tokyo Declaration at the time of a summit with Russian President Boris Yeltsin.

Japan's first National Security Strategy, which the Cabinet headed by Prime Minister Shinzo Abe approved in 2013, also reconfirmed it and called it Japan's "consistent policy."

The Soviet Union seized the four islands after it entered the war against Japan during the closing days of World War II. Diplomatic relations were restored when Prime Minister Ichiro Hatoyama visited the Soviet Union and signed the Japan-Soviet Joint Declaration in 1956.

The Soviet Union was dissolved in 1991, whereupon Russia became Japan's counterpart in the territorial talks. Russian President Vladimir Putin agreed with Abe, during his visit to Japan in 2016, that both countries should start talks toward conducting joint economic activities on the four islands.

In the meantime, Tokyo has declined to disclose records of its talks on the Northern Territories, including those dating from the time of the Soviet Union, on grounds that negotiations are still continuing with Russia.

"We are not in a position to comment on a document owned by the private sector," a Foreign Ministry representative said with regard to the newfound proceedings.