Russia is considering building a naval base on islands off northern Japan, an area that includes territory at the center of a long-running spat between Tokyo and Moscow, the TASS news agency reported Friday, quoting Russian Defense Minister Sergei Shoigu.

Shoigu’s assertion of Russian sovereignty over the Greater Kuril Ridge, which includes part of the Japan-claimed islands, comes as Prime Minister Shinzo Abe is expected to visit Russia in May to meet with President Vladimir Putin in the hope of making progress in negotiations over the dispute.

According to the report, Shoigu said during a Defense Ministry board meeting that an investigative team from the Russian Pacific Fleet will be dispatched next month for a three-month mission to determine the feasibility of building a base somewhere on the islands.

Shoigu also announced Friday that Bal and Bastion shore-to-ship missiles and Eleron-3 drones will be deployed on the islands before the end of this year, TASS said.

The row over four Russian-held islands claimed by Japan has prevented the two countries from signing a peace treaty following World War II.

The islands — Etorofu, Kunashiri, Shikotan and the Habomai group of islets — were seized by the Soviet Union following Japan’s surrender in August 1945. The islands are called the Northern Territories in Japan and the Southern Kurils in Russia.

Japan has been fighting for recognition of its ownership of the islands, while Russia maintains it will return Shikotan and the Habomai islets following the conclusion of a postwar peace treaty.

The Greater Kuril Ridge includes Etorofu and Kunashiri, and Shoigu’s remarks apparently underscored Russia’s position that it sees no room for compromise over the two islands.