Saudi Arabia, which is hosting this year's virtual summit, opened up the two-day meeting urging leaders to mount a global response to the coronavirus pandemic.
The leaders spoke after a virtual G-20 meeting. President Trump called it a "very good conversation," and China state TV said Xi Jinping offered to help the U.S. respond to the spread of the virus.
President Trump will meet with Indian Prime Minister Narendra Modi at the G-20. Trade tensions threaten to overshadow progress in strategic ties, former State Department official Alyssa Ayres writes.
President Trump is due to meet with Chinese leader Xi Jinping this weekend, raising hopes the two leaders might call a truce in their trade war. The White House has downplayed expectations of a deal.
The deal pauses a tariff increase that had been planned to take effect New Year's Day. President Trump called the meeting with China's president "amazing and productive."
The president cited Russian aggression against Ukraine in his tweet about the change. He still has a series of meetings planned on the sidelines of the summit, including with China's Xi Jinping.
Demonstrators threw bottles and stones, and police responded by firing water cannons and using pepper spray. Organizers canceled one protest march because of the violence.
Cancer specialists from the United States, Germany and other countries will join the medical team treating a political dissident detained by China since 2008. He has late-stage liver cancer.
The president met with Vladimir Putin on the sidelines of the G-20 summit. On Monday, Obama said their negotiations were unsuccessful. The same day, bombings in Syria killed more than 50 people.
In a historic step towards rebuilding relations with the poor, heavily-bombed nation, the president will join other world leaders there, after wrapping another big global meeting in Hangzhou, China.