Arvind Panagariya, sherpa for India at the Summit, tweeted about the "interaction", along with pictures of the two leaders and others just before start of the second day of working sessions of the G20 Summit ending today.
"In an impromptu interaction at the G20 Summit, POTUS (President of the US) waves to the PM, walks to him, other leaders gather around. Gr8 moments," Panagariya tweeted.
He further described the interaction as "some memorable moments just before the second day of the G20 Summit begins".
Besides a series of bilateral meetings, Modi had brief chats with various leaders at the Summit, including with IMF chief Christine Lagarde and German Chancellor Angela Merkel.