Rio de Janeiro, Brazil - BRICS leaders descended on sunny Rio de Janeiro Sunday, issuing a dark warning that US President Donald Trump's "indiscriminate" import tariffs risk hurting the global economy.

The 11 emerging nations – including Brazil, Russia, India, China, and South Africa – represent about half the world's population and 40% of global economic output.

The bloc is divided about much, but found common cause when it comes to the mercurial US leader and his stop-start tariff wars.

The BRICS leaders voiced "serious concerns about the rise of unilateral tariff and non-tariff measures," warning they are illegal and arbitrary, according to a final summit statement.

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In April, Trump threatened allies and rivals alike with a slew of punitive duties, but abruptly offered a reprieve in the face of a fierce market sell-off.

Trump has warned they will again impose unilateral levies on partners unless they reach "deals" by August 1.

The BRICS said such moves break world trade rules, threaten to further reduce global trade, and were "affecting prospects for global economic development."

The summit declaration did not mention the US or its president by name, but it is a clear political volley directed at the occupant of 1600 Pennsylvania Avenue.

The Peterson Institute for International Economics, a Washington think tank, estimates Trump's tariffs could trim about two points off US GDP and hit economies from Mexico to the oil-rich Arabian Gulf.

Conceived two decades ago as a forum for fast-growing economies, the BRICS have come to be seen as a Chinese-driven counterbalance to Western power.

But as the group has expanded to include Iran, Indonesia, and others, it has struggled to reach meaningful consensus on issues ranging from the Israel-Gaza war to reforming international institutions.

The political punch of this year's summit has been depleted by the absence of China's Xi Jinping, who is skipping the meeting for the first time in his 12 years as president.

The Chinese leader will not be the only notable absentee. Russian President Vladimir Putin, charged with war crimes in Ukraine by the International Criminal Court (ICC), is also opting to stay away, but participated via video link.