Former Prime Minister Yoshihiko Noda has expressed concern over Prime Minister Shinzo Abe's negotiations with Russia for a postwar peace treaty, saying Moscow is unlikely to be very flexible.

Speaking to reporters in Ishikawa Prefecture on Sunday, Noda, who is secretary-general of the Democratic Party, said, "We should avoid being too eager (to resolve the peace treaty issue) and allow only Russia to gain benefits from economic cooperation (with Japan)."

The Abe government is keen to achieve a breakthrough in the long-standing dispute over Russian-held, Japanese-claimed islands off Hokkaido that has prevented the two countries from concluding a post-World War II peace treaty.

Abe has proposed a batch of economic cooperation plans with Russia in an apparent effort to encourage Moscow to soften its stance on the territorial dispute.

Noda made the remarks after Foreign Minister Fumio Kishida and his Russian counterpart, Sergey Lavrov, held talks in Moscow. After the meeting, Lavrov moved to allay expectations of immediate progress in settling the peace treaty issue, saying, "The problem is complicated."

Russia President Vladimir Putin is scheduled to visit Japan for talks with Abe on Dec. 15 and 16.