Russian President Vladimir Putin said Thursday that the United States’ military presence in Japan was complicating the search for a formal peace treaty between Moscow and Tokyo.

Russia and Japan have been in dispute for seven decades over a group of islands captured by Soviet troops in the last days of World War II. As a result, they have still not formally ended hostilities.

Putin told reporters at his annual news conference that Moscow was concerned by the deployment of a U.S. air defense system in Japan, presumably referring to the Aegis Ashore anti-missile defense system.

He said Russia does “not regard (the missile system) as defensive weapons but they are part of the U.S. strategic potential.”

Putin also pointed out the Japanese government is building an alternative base for U.S. Marine Corps Air Station Futenma, now located in central Okinawa, in the Henoko district of Nago further north, despite strong opposition from local residents and Okinawa Gov. Denny Tamaki.

“The U.S. base on Okinawa has been there for decades now. … We don’t understand the level of sovereignty Japan has when such decisions are made,” Putin said.

“What will happen after a peace agreement is signed, we don’t know. But without an answer to this question, it will be very difficult for us to take any major decisions.”

“I am convinced — and Prime Minister (Shinzo) Abe agrees — the current situation is not normal. Russia and Japan are both interested in the complete normalization of our relations.”

Abe and Putin agreed in November to step up peace treaty talks based on a 1956 agreement, in which the Soviet Union agreed to hand over Shikotan and the Habomai islet group to Japan once a peace treaty had been signed.

The former Soviet Union seized the islands, along with Etorofu and Kunashiri islands, known as the Northern Territories in Japan and the Southern Kurils in Russia, after Japan’s surrender in World War II in 1945.

As the territorial dispute over the islands has prevented the two nations from concluding a peace treaty, Abe is expected to visit Russia for another summit with Putin in January.

On the U.S. threat to quit the Intermediate-range Nuclear Forces Treaty, Putin also said: “We are essentially witnessing the breakdown of the international arms control order and (the start of) an arms race.”

“It’s very hard to imagine how the situation will develop (if the U.S. quits the treaty). If these missiles appear in Europe what should we do? Of course, we’ll have to ensure our own security.”