Prime Minister Narendra Modi is likely to meet Chinese President Xi Jinping on the sidelines of the G-20 Summit on July 7 in Hamburg, Germany, amid escalating tensions between both nations.
The German leader, who faces elections in September, has expressed her disappointment with the United States decision to pull out of the Paris climate accord and become more protectionist on trade.
The Group of 20 (G20) comprises leaders of the world's major industrialized and emerging economies.
Merkel's first meeting with the US president in March turned awkward when Trump appeared to decline to shake her hand. Meanwhile, Merkel's ruling party, the CDU, recently stripped language from its campaign platform that described the United States as a "friend" and the "cornerstone" of German worldwide relations.
"We are living in the era of global interdependency, human civilization depends on global commons as the climate system, the oceans, global resources, are stability of worldwide financial markets", Messner said. The site is less than a mile from where the G20 leaders will be meeting.
The BRICS leaders' informal meet will at least ensure the two leaders meet away from the formal G20 summit and give them the opportunity to directly speak to each other.
And World Bank President Jim Yong Kim told Handelsblatt he agreed with Ms Merkel on climate change, saying: "We can not wait".
"It is, for example, open whether we can and should in the future rely on the USA investing so much as it has so far in the United Nations' work, in Middle East policy, in European security policy or in peace missions in Africa", Merkel said, according to Associated Press.
The gathering outside city hall took place in parallel with protests by canoeists on the nearby river Alster, while in the port of Hamburg, Greenpeace staged a climate demonstration near a ship laden with coal. Already, German police have used water cannon to disperse around 500 anti-capitalist protesters.
Earlier Sunday, about 10,000 people marched peacefully through Hamburg streets.
She told the newspaper Die Zeit that as G20 president, she had to work on reaching agreement rather than contributing "to a situation where a lack of communication prevails".
Officials estimate that some 8,000 protesters from Europe's violent left-wing scene to be on hand and have been tracking known activists coming in from Scandinavia, Switzerland, Italy and elsewhere, Hamburg police chief Ralf Martin Meyer said.