MOSCOW (AP) — Russia’s foreign minister says the U.S.-Japan security alliance poses “a problem” for Russia-Japan relations and complicates peace treaty talks.

The two countries have been struggling to negotiate a peace treaty after World War II because of a territorial dispute. The Soviet Union took the four southernmost Kuril Islands during the final days of the war, which Japan asserts territorial rights to.

Russian Foreign Minister Sergey Lavrov said Saturday that Japan’s “military alliance with Washington, of course, is a problem” when it comes to changing the nature of the country’s relationship with Russia.

Lavrov said the Japanese government promised to address Russia’s concerns.

He added that implementation of the 1956 Soviet-Japanese Declaration, which outlined conditions for a peace treaty, was not possible with the U.S. military presence in Japan.