U.S. President Barack Obama and Russian President Vladimir Putin spoke briefly on the sidelines of APEC summit events on Monday night but did not delve into the issues that divide their two countries, according to U.S. and Russian officials.

The informal contact between the two leaders, who have been deeply at odds over Russia's role in the Ukraine conflict and its backing for Syrian President Bashar Assad, took place during events to welcome participants to the Chinese-hosted summit.

Both sides played down the significance of the moment. "They only had a brief encounter where they didn't have time to cover issues," a senior U.S. official said. "We'll let you know if they interact/cover issues tomorrow."