The group of emerging economies met via videoconference at the initiative of Brazil's President Luiz Inacio Lula da Silva, whose office said it was necessary to address the "intensification of unilateral measures."

The BRICS represents nearly 40 percent of global GDP and almost half of the world's population. 

Its members are among those hardest hit by what Lula referred to Monday as "tariff blackmail" and "unjustified and illegal" trade practices.

Chinese President Xi Jinping, for his part, called for the upholding of "the multilateral trading system with the World Trade Organization at its core" and for rejection of "all forms of protectionism."

Tensions between the United States and China, the world's two biggest economies, resulted in tit-for-tat duties that reached triple digits earlier this year before being lowered again.

In Brazil's case, Trump slapped his highest level of trade tariff -- 50 percent -- on a range of goods from Latin America's biggest economy.

Trump is punishing Brazil for what he calls a "witch hunt" against his right-wing ally, former president Jair Bolsonaro who is on trial for allegedly plotting a coup to take power back from Lula after losing 2022 elections.

A verdict in the trial is expected this week.

"Tariff blackmail is being normalized as an instrument to conquer markets and interfere in domestic affairs," Lula said Monday.

'Great hardships' 

Washington also imposed tariffs of up to 50 percent on Indian imports, accusing New Delhi of fueling Moscow's deadly attacks on Ukraine by purchasing Russian oil.

Indian Foreign Minister Subrahmanyam Jaishankar told the BRICS summit the world needed sustainable trade, adding that "increasing barriers and complicating transactions will not help."

Russian President Vladimir Putin also took part in the virtual meeting days after gathering with Xi, North Korea's Kim Jong Un and India's Narendra Modi in China, where regional leaders slammed America's "bullying behavior."

Trump hit South Africa, engaged in a spat with Washington over a range of domestic and international policies, with a 30 percent tariff -- the highest in sub-Saharan Africa.

Trump, who has repeatedly cited debunked claims of a "genocide" of white South Africans, will not attend the G20 summit in Johannesburg later this year.

South African President Cyril Ramaphosa, in a prepared speech, told BRICS counterparts that "unilateral tariff actions are contributing to an increasingly protectionist environment which poses great hardships and danger for the countries of the Global South."

In July, Trump lashed out at the BRICS and threatened its members with additional export duties after they voiced concern that his trade war was putting the global economy at risk.

"We must remain steadfast in promoting the building of an open global economy, sharing opportunities and achieving win-win results through openness," Xi underscored Monday.

Other BRICS members are Indonesia, Egypt, Ethiopia, Iran, Saudi Arabia and the United Arab Emirates. 

Lula also used the summit to denounce a US military build-up in the Caribbean, which he said added "a factor of tension."

Washington has deployed warships and aircraft in what it labeled an anti-drug operation, and blew up an alleged narco boat, killing 11 people and raising fears in Venezuela of an invasion.