The BRICS nations of Brazil, Russia, India, China and South Africa represent a quarter of the global economy, and interest in joining the group surged ahead of its three-day summit in Johannesburg.
Security has been bolstered across the city where South African President Cyril Ramaphosa is hosting China's President Xi Jinping, Indian Prime Minister Narendra Modi, Brazil's President Luiz Inacio Lula da Silva and some 50 other leaders.
Russian President Vladimir Putin, who is the target of an international arrest warrant over alleged war crimes in Ukraine, did not attend in person and addressed the summit via pre-recorded video.
Russia will be represented in Johannesburg by Foreign Minister Sergei Lavrov.
Putin said the BRICS grouping of countries was on course to meet the aspirations of most of the world's population, according to recorded remarks at the summit.
"We cooperate on the principles of equality, partnership support, respect for each other’s interests, and this is the essence of the future-oriented strategic course of our association, a course that meets the aspirations of the main part of the world community, the so-called global majority," Putin said.
Spotlight on Ukraine
Representing 40% of the world's population, and democratic and authoritarian states at varying levels of economic growth, the BRICS nations share a common desire for a global order they see as better reflecting their interests and rising clout.
BRICS is also championing its own development bank as an alternative to the World Bank and International Monetary Fund, and proposals to reduce the use of the U.S. dollar in global trade.
"We are only saying that we exist, we are organizing ourselves, and we want to sit at the negotiating table on an equal footing with the European Union, the United States or any other country," Lula said in a social media post on Tuesday.
The theme of its 15th summit is "BRICS and Africa" and comes as the continent emerges as a renewed diplomatic battleground with the United States, Russia and China jostling for influence.
The summit has underscored divisions over the war in Ukraine and the support Russia enjoys from its other BRICS partners at a time of global isolation.
South Africa, China and India have not condemned Russia's invasion while Brazil has refused to join Western nations in sending arms to Ukraine or imposing sanctions on Moscow.
Ahead of the summit, Ramaphosa said his country would "not be drawn into a contest between global powers."
In a park near the summit venue, two dozen protesters held up blue and yellow Ukrainian flags and placards reading "Go home Lavrov."
'Importance, stature, influence'
The bloc began as four nations in 2009 but expanded the following year with the addition of South Africa.
Officials say more than 40 countries have shown interest in joining from across the "Global South," a broad term referring to nations outside the West.
Like the BRICS themselves, these countries run the gamut and include traditionally non-aligned nations like Indonesia and others that are openly hostile to the United States and its allies, like Iran.
"It goes to show that the BRICS family is growing in its importance, in its stature and also in its influence in the world," said Ramaphosa.
South Africa will present BRICS leaders with a proposal to expand its membership.
But the issue divides China and its regional rival India, which is wary of Beijing shaping the forum to suit its own geo-politial agenda as it competes for global influence against the United States.
The leaders met on Tuesday on the topic but divisions re-emerged ahead of the critical debate over a potential expansion of the group intended to boost its global clout.
Xi skipped the event, despite the presence there of counterparts Ramaphosa, Lula and Modi.
His remarks were delivered by Chinese Commerce Minister Wang Wentao, and it was not immediately clear why Xi, who had a meeting with host Ramaphosa earlier in the day, did not attend.
Brazil's Lula said he supported the entry of "several countries" including Argentina.
"It is very important for Argentina to be in BRICS," Lula said in a live broadcast on social media.
Argentina, whose largest trade partner is Brazil, has previously said it intended to join the BRICS bloc.
Analysts say when considering new members, South Africa, India and Brazil must balance a desire for warm ties with China and Russia against the risk of estranging a major trading partner in the United States.
Information for this report came from AFP and Reuters.