WASHINGTON/BRASILIA (Reuters) -President Donald Trump said on Wednesday that the U.S. would impose a 50% tariff on all imports from Brazil after a public spat this week with his Brazilian counterpart who called him an unwanted "emperor."

In a letter, Trump linked the tariffs to Brazil's treatment of former President Jair Bolsonaro who is on trial over charges of plotting a coup.

The levies were imposed due "in part to Brazil's insidious attacks on Free Elections, and the fundamental Free Speech Rights of Americans," the letter said.

Brazil's real currency added to earlier losses to fall over 2% against the dollar after the announcement.

The U.S. is Brazil's second largest trading partner after China and the tariffs are a major increase on the 10% that were announced in April.

Trump's letter said the 50% tariff will start Aug. 1 and be separate from all sectoral tariffs. It added that Trump directed U.S. Trade Representative James Greer to initiate a probe into what he called unfair trade practices by Brazil, particularly on U.S. companies' digital trade.

On Monday, Brazil's President Luiz Inacio Lula da Silva attacked Trump after the U.S. leader had threatened imposing an additional 10% tariff on the BRICS group of developing nations which he called "anti-American."

"The world has changed. We don't want an emperor," Lula told reporters when asked about the possible BRICS tariff.

"We are sovereign nations," Lula added. "If he thinks he can impose tariffs, other countries have the right to impose tariffs too."

BOLSONARO 'WITCH HUNT'

Tensions between the United States and Brazil had already been intensifying on Wednesday after Brazil's foreign ministry summoned the U.S. Embassy's chargé d'affaires over a statement defending Bolsonaro.

Around the same time, Trump, speaking to reporters at an event with West African leaders at the White House, said Brazil "has not been good to us, not good at all," adding that the tariff rates would be based on "very, very substantial facts" and past history.

The U.S. Embassy in Brasilia confirmed on Wednesday that Gabriel Escobar, its chargé d'affaires, had a meeting with officials from Brazil's foreign ministry, though it declined to share details about the conversation. The ministry didn't respond to a request for comment.

Trump's support for Bolsonaro echoed his support for other global right-wing leaders who have faced domestic legal cases like French far-right leader Marine Le Pen and Israeli Prime Minister Benjamin Netanyahu. Trump has called cases against those leaders a "witch hunt," a term he commonly used for cases that he faced himself in the U.S. after the end of his first time in office.

Trump said in a social media post on Monday that Bolsonaro was the victim of a "witch hunt." The American Embassy in Brasilia issued a statement on Wednesday to the local press echoing his remarks.

"The political persecution of Jair Bolsonaro, his family and his supporters is shameful and disrespectful of Brazil's democratic traditions," the U.S. Embassy's press office said in a statement in Portuguese.