Russia “cannot” cede the sovereignty of the Japanese-claimed islands off Hokkaido, the speaker of the Russian parliament’s upper house said.

Valentina Matviyenko, speaker of the Federation Council, told a news conference in Tokyo on Tuesday that Japan is welcome to participate in joint economic activities on the islands, but these “must be carried out under Russian sovereignty and law.”

The issue of sovereignty over the island chain, called the Northern Territories in Japan and the Southern Kurils in Russia, has kept the countries from concluding a post-World War II peace treaty.

With Prime Minister Shinzo Abe and President Vladimir Putin set to hold talks in Japan on Dec. 15, speculation has been growing that they could be gearing up for a deal over the peace treaty and the islands.

Abe proposed to Putin during talks in May an eight-point economic cooperation plan, including assistance in energy development and the industrialization of the Russian Far East.

The Abe government has said it will continue to steadfastly proceed with negotiations toward a resolution of the territorial row and the prompt conclusion of a peace treaty, while Putin said last week that no time frame should be set for concluding the treaty.

Matviyenko, who is reportedly close to Putin, met Abe earlier Tuesday. Speaking to reporters after the meeting, she only said that they exchanged views on Japan-Russia relations in general and preparations for Putin’s visit next month.