By Lisandra Paraguassu RIO DE JANEIRO -Leaders of the growing BRICS group of developing nations were set to gather in Rio de Janeiro on Sunday, calling for reform of traditional Western institutions while presenting the bloc as a defender of multilateralism in an increasingly fractured world.

BRICS leaders set to discuss key global political issues in Rio de Janeiro, but questions over the bloc’s cohesion arise as Chinese President Xi Jinping and Russian President Vladimir Putin opt to skip the summit.

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. In April, Trump threatened allies and rivals alike with a slew of punitive duties, but abruptly offered a reprieve in the face of a fierce market sell-off.