SAO PAULO (AP) — Brazil’s Foreign Ministry said on Saturday it denied visas to two U.S. State Department officials that sought to travel to the South American nation next week, in the latest political barb between the two countries.

The move became public after The Washington Post reported the Brazilian government saying the officials, Riley M. Barnes, an assistant secretary, and Samuel Samson, a deputy assistant, wanted to cast doubt on the upcoming October elections in Brazil.

A spokesperson for Brazil’s foreign office said Barnes and Samson requested visas on July 20 and they were denied Friday. He did not disclose the reasons behind the decision.

Brazilian President Luiz Inácio Lula da Silva will bid for reelection against Sen. Flávio Bolsonaro, whose family has many ties with the Trump administration.

Sen. Bolsonaro and his brother, Eduardo, visited U.S. officials in Washington, including U.S. President Donald Trump, in late May. Shortly afterward, the Trump administration classified Brazil’s biggest drug-trafficking groups — First Command Capital and Red Command — as foreign terrorist organizations, a move Lula opposes.

The Trump administration also imposed an up to 37.5% tariff hike on thousands of Brazilian exports, which came into force Friday. The U.S. government claims the South American nation has unfair competition practices and fails to stop forced labor practices — both accusations rejected by the Lula administration as an attempt to sway the election to Sen. Bolsonaro.

The U.S. State Department said Barnes and Samson planned to go to Brasilia July 27-30 to meet government officials, religious leaders and others about “election integrity,” religious freedom and freedom of expression. The department, in response to a query from The Associated Press, called it a routine visit and said that “any insinuation of a ‘ploy’ to undermine a democratic nation’s election is a baseless lie.”

Former Brazilian President Jair Bolsonaro has for years fed concerns about the country’s electronic voting system, without providing any evidence for his claims. He is now serving a 27-year prison sentence at home for an attempted coup. He has long insisted that the machines, used for a quarter-century, are prone to fraud.

His son, Sen. Bolsonaro, has recently repeated some of these claims, although he steered clear of those on Saturday when his Liberal Party confirmed him as a presidential candidate in Sao Paulo.