China is seeking to rapidly grow the club of large emerging economies amid rising competition with the United States, and more than 40 nations are lining up to join,
France 24 reports.
But the BRICS other major power, India, is wary of rushing to expand and the divisive issue tops the agenda as it discusses its future at a three-day summit in Johannesburg.
The BRICS nations -- Brazil, Russia, India, China and South Africa -- represent 40 percent of the world's population and a quarter of the global economy.
A disparate association of big and small economies, democratic and authoritarian states, the BRICS share a common vision for an alternative to the Western-led world order that better serves developing nations.
"The world is changing," said South African President Cyril Ramaphosa at the opening of the plenary session of the BRICS on Wednesday.
"New realities call for a fundamental reform of the institutions of global governance so that they may be more representative and better able to respond to the challenges that confront humanity."
The other BRICS leaders of Brazil, India and China are also present for the summit, which is being attended by 50 other heads of state and government.
Russian President Vladimir Putin, who faces an international arrest warrant over alleged war crimes in Ukraine, did not attend in person and addressed the summit via video link.
Chinese President Xi Jinping told delegates on Monday that the "course of history will be shaped by the choices we make".
But the head of the BRICS most powerful state said the summit was "not an exercise of asking countries to take sides, nor an exercise of creating bloc confrontation".
"Rather, it is an endeavour to expand the architecture of peace and development," Xi said in remarks delivered on his behalf by his Commerce Minister Wang Wentao.
