The United States has launched an investigation into “unfair” trading practices by Brazil, escalating President Donald Trump’s spat with the world’s 10th-largest economy over issues including the criminal case against its former President Jair Bolsonaro.

A US trade probe suddenly ordered by President Donald Trump on Brazil sent shockwaves through President Luiz Inacio da Silva’s government, according to a senior Brazilian diplomat who described it as an unwarranted threat that has helped to plunge relations to their lowest point in over a century.

The probe will determine if Brazil's economic policies and practices in a number of areas are "unreasonable or discriminatory and burden or restrict US commerce," the Office of the US Trade Representative said in a statement.