The Japanese prime minister expects to raise the issue of signing a peace treaty with Russia during talks with Vladimir Putin.
During a joint news conference with NATO Secretary General Jens Stoltenberg, US President Donald Trump said Washington's relations with Moscow are at an "all time low," adding, "We're not getting along with Russia at all."
Russia's force in Syria has suffered losses since late January more than three times higher than the official toll, according to evidence gathered by Reuters, a tally that shows the fight in Syria is tougher and more costly than the Kremlin has disclosed.
Russia said on Tuesday that a U.S. decision to ease restrictions on arming Syrian rebels had opened the way for deliveries of shoulder-fired anti-aircraft missiles, a move it said would directly threaten Russian forces in Syria.
Backed by ships, helicopters and drones, Russian rescue teams searched Sunday for victims after a Russian plane carrying 92 people to Syria crashed into the Black Sea shortly after takeoff. Investigators said they were looking into every possible cause for the crash, including a terror attack.