The Trump administration said on Wednesday that it would impose a new 25 percent tariff on Brazil next week, arguing that the country had adopted a range of unfair trade practices against the United States.

The tariff will apply to thousands of Brazilian products, but will exempt several major categories of exports, including oil and gas, beef, coffee, oranges, and aircraft parts. The tariff will apply to Brazilian ethanol, a senior administration official said, and take effect next Wednesday.

Before the announcement, a Brazilian government official said the country had not ruled out its own retaliatory measures.

The administration put a 40 percent tariff on many Brazilian exports last year. But President Trump walked some of the tariffs back in an executive order in November after a meeting with Brazil’s president, Luiz Inácio Lula da Silva.

Then in February, the Supreme Court ruled that Mr. Trump’s use of an emergency law to impose those tariffs was unlawful, forcing him to remove the remaining tariffs on Brazil and other countries. The administration imposed a 10 percent tariff on almost all imports as a stopgap measure, but that tariff will expire this month.

The Trump administration initiated an investigation into Brazil’s trade practices last July under a different law, known as Section 301, which is what it will use to impose the tariff next week. The administration is also using Section 301 to prepare two other slates of tariffs, which are likely to be imposed on dozens of countries, potentially including more tariffs on Brazil.

Mr. Trump’s tariffs on Brazil last year were partly an effort to help a political ally, Jair Bolsonaro, the country’s former right-wing president, avoid a jail sentence over his bid to cling to power after he lost the presidential election in 2022.

The effects of those tariffs were muted because many of Brazil’s most important exports to the United States were granted exemptions. And soon after Mr. Bolsonaro was sentenced to nearly three decades in prison, most of the levies were dropped.

Even as diplomatic relations between the Western Hemisphere’s two most populous nations began to normalize, the United States continued to investigate Brazil’s trade practices.

The United States consistently exports more to Brazil than it imports, sending petroleum, machinery and aircraft parts. But it accuses Brazil of unfairly shielding its domestic industries and failing to take sufficient measures to combat corruption and bribery as well as enforce intellectual property laws.

It has also pointed to inadequate policing of deforestation, even as data shows that Brazil has slashed rates of forest destruction drastically in recent years, from record levels under Mr. Bolsonaro.

Another target of the Trump administration has been Brazil’s digital payment system, which the United States accuses of unfairly undercutting U.S. financial and technology companies like Visa and Apple.

A senior administration official said Brazilian courts had issued sealed orders directing U.S. social media companies to take down certain political content. The official also said Brazil had offered Mexico and India preferential trade terms that it was refusing to extend to the United States.

The new tariff is likely to become a political issue in Brazil before the presidential election in October. Mr. Lula will seek another term, going up against one of Mr. Bolsonaro’s sons, Flávio, at the polls.

Mr. Lula has blamed the Bolsonaros, including another of Mr. Bolsonaro’s sons, for the threat of more tariffs. That son, who is living in the United States, aggressively lobbied Mr. Trump last year to help his father by pressuring Brazil to drop the case against him.

Flávio Bolsonaro has also made several trips to Washington to ask the Trump administration to help his conservative movement, although he has said he never asked for tariffs to be applied to his country. In recent weeks, as his support has slipped in early polling, he has tried to distance himself from the tariffs and asked the Trump administration to hold off on applying them until after the election.

Meanwhile, diplomatic tensions with Mr. Trump have helped boost Mr. Lula’s popularity. The Brazilian leader has called the economic measures politically motivated, accusing Mr. Trump of threatening his country’s sovereignty.