As world leaders gathered in Hamburg for the G20 summit, German Chancellor Angela Merkel was facing the daunting task of steering her guests towards agreeing on many issues.
Russian President Vladimir Putin met his US counterpart briefly on Friday.
President Donald Trump said he had been looking forward to meeting Putin.
The two leaders were expected to discuss the conflicts in Syria and Ukraine, terrorism, security and bilateral issues.
They reportedly planned to talk about the return to Russia of diplomatic compounds in the US states of Maryland and New York seized by the Obama administration.
British Prime Minister Theresa May said G20 leaders would urge Trump to reconsider his decision to pull out of the Paris climate deal.
May was also expected to hold a bilateral meeting with Trump on the sidelines of the G20 meeting on Friday.