Abe, Putin likely to meet in Sochi in early May: source

The meeting is expected to be officially agreed on at a meeting Friday in Tokyo between Japanese Foreign Minister Fumio Kishida and his Russian counterpart Sergey Lavrov, according to the source.

The agenda of that meeting, announced earlier in the day, is expected to also include the Ukraine situation.

Work on improving Russo-Japanese ties stalled after Russia annexed the Crimea region in southern Ukraine in 2014 and intervened in a conflict in eastern Ukraine between government forces and pro-Russian separatists. Last October, however, Tokyo and Moscow resumed high-level negotiations over a long-standing territorial dispute.

The dispute over four Russian-held islands off Hokkaido, called the Northern Territories in Japan and the Southern Kurils in Russia, has prevented the two countries from concluding a post-World War II peace treaty.

"With an eye on a dialogue between the country leaders, I hope to hold substantial discussions on the overall Japan-Russia relations, including the signing of a peace treaty," Kishida told a press conference.

Kishida and Lavrov are also expected to discuss a Putin visit to Japan, which Tokyo initially hoped to realize in 2014 only to see it postponed due to tensions over Ukraine and other issues.

The Abe government is eager to realize Putin's trip, seeing it as a chance to advance talks on the territorial row.