The 11 emerging nations -- including Brazil, Russia, India, China and South Africa -- account for about half the world's population and 40 percent of global economic output.

President Donald Trump said the U.S. will impose an additional 10% tariff on any countries aligning themselves with the "Anti-American policies" of the BRICS group of developing nations, whose leaders kicked off a summit in Brazil on Sunday.

The BRICS leaders voiced "serious concerns about the rise of unilateral tariff and non-tariff measures," warning they are illegal and arbitrary, according to a final summit statement.