Russian President Vladimir Putin, who faces an international arrest warrant over alleged war crimes in Ukraine, will not join leaders from Brazil, India, China and South Africa amid rifts over whether to expand the bloc to include dozens of "Global South" nations queuing up to join.

South Africa will host Chinese President Xi Jinping, Brazil's Luiz Inacio Lula da Silva and Indian Prime Minister Narendra Modi for the BRICS summit from August 22 to 24.

Spread over the globe and with economies that operate in vastly different ways, the main thing uniting the BRICS is scepticism about a world order they see as serving the interests of the United States and its rich-country allies who promote international norms they enforce but don't always respect.

Few details have emerged about what they plan to discuss, but expansion is expected to be high on the agenda, as some 40 nations have shown interest in joining, either formally or informally, according to South Africa. They include Saudi Arabia, Argentina and Egypt.

"BRICS AND AFRICA"

China, seeking to expand its geopolitical influence as its tussles with the United States, wants to enlarge BRICS quickly, while Brazil is resisting expansion, fearing the already unwieldy club could see its stature diluted by it.

In a written response to Reuters questions, China's foreign ministry said it "supports progress in expanding membership, and welcomes more like-minded partners to join the 'BRICS family' at an early date."

Russia needs friends to counter its diplomatic isolation over Ukraine, and so is keen to bring in new members, as is its most important African ally, South Africa.

India is on the fence.

In a nod to the bloc's African hosts, the theme of its 15th summit is "BRICS and Africa", emphasising how the bloc can build ties with a continent increasingly becoming a theatre for competition between world powers.

South Africa's foreign minister Naledi Pandor in a statement last week said BRICS nations wanted to show "global leadership in addressing the needs ... of the majority of the world, namely ... development and inclusion of the Global South in multilateral systems," in a veiled swipe at Western dominance.

BRICS nations are keen to project themselves as alternative development partners to the West. China's foreign ministry said BRICS sought to "reform global governance systems (to) increase the representation ... of developing countries and emerging markets."

The bloc's New Development Bank (NDB) wants to de-dollarise finance and offer an alternative to the much-criticised Breton Woods institutions.

But it has approved only $33 billion of loans in nearly a decade -- about a third of the amount the World Bank committed to disbursing just last year -- and has recently been hobbled by sanctions on member Russia.

South African officials say talk of a BRICS currency, mooted by Brazil earlier this year as an alternative to dollar-dependence, is off the table.

With 40% of global population, the BRICS carbon-intensive nations also make up about the same share of greenhouse gas emissions. Officials in Brazil, China and South Africa said climate change may come up but indicated it wouldn't be a priority.

BRICS countries blame rich nations for causing most global warming and want them to take on more of the burden of decarbonising the world's energy supply. China was accused of blocking climate discussions at the G20, which it denied.