Why has Brazil accused the US of election interference?

In Brazil’s upcoming presidential election, President Luiz Inácio Lula da Silva is facing right-wing challenger and ally of Donald Trump, Flavio Bolsonaro, son of former President Jair Bolsonaro.Washington has backed closer ties with Brazil’s right wing, while Lula da Silva has accused Bolsonaro’s camp of encouraging foreign interference.The election has raised questions about US influence, trade tariffs, organised crime and Brazil’s sovereignty.The BBC’s Ione Wells explains.