The bloc, consisting of Brazil, Russia, India, China and South Africa, is holding its first in-person meeting since before the COVID-19 pandemic, but Putin will participate via video call after his travel to South Africa was complicated by an International Criminal Court arrest warrant issued for him in March over the abduction of children from Ukraine.
Xi, Brazilian President Luiz Inácio Lula da Silva, Indian Prime Minister Narendra Modi and South African President Cyril Ramaphosa will attend in person as the bloc — home to 40% of the world's population and responsible for more than 30% of global economic output mulls a possible expansion.
That will top the agenda at Wednesday's main summit meeting in Johannesburg's financial district of Sandton.
More than 20 nations have applied to join the bloc, according to South African officials, including Saudi Arabia, Iran and the United Arab Emirates.
The five BRICS countries will have to agree on the criteria for new members before any countries are admitted, but a bigger BRICS is seen as a policy favored by China and Russia amid their deteriorating relations with the West.
The BRICS group was formed in 2009 by Brazil, Russia, India and China. South Africa was added in 2010.
South African Minister of Trade and Industry Ebrahim Patel officially opened the summit Tuesday, welcoming about 1,200 delegates from the five BRICS nations but also from dozens of other developing countries.
More than 40 heads of state are expected at the three-day meeting, according to Ramaphosa.
Kremlin spokesperson Dmitry Peskov has stressed that Putin will fully participate despite appearing virtually and will make a speech. Russia will also be represented in person by Foreign Minister Sergey Lavrov.
United Nations Secretary-General António Guterres also is expected to attend.
The summit officially began with a business forum on Tuesday morning, and Xi, Lula, Modi and Ramaphosa were expected to arrive at the Sandton Convention Centre for the first meeting of the leaders in the afternoon.
They will also hold a retreat Tuesday evening at the luxury Summer Place estate in Johannesburg's plush Hyde Park suburb.
Xi, who has gradually resumed foreign travel after the lifting of his country's strict COVID-19 regulations, was to meet with Ramaphosa for a state visit in the South African capital, Pretoria, on Tuesday morning.
He will then travel 60 kilometers (37 miles) through South Africa's most important economic province of Gauteng to the summit in Johannesburg.
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