WASHINGTON — The United States accused President Nicolás Maduro of Venezuela on Friday of trying to rig a coming election for control of his country’s parliament, either by detaining opposition leaders or bribing lawmakers with up to $500,000 for each vote.

Thirty lawmakers in Venezuela’s National Assembly have had their legal immunity stripped by Mr. Maduro’s government over the past year, according to a United Nations report this week, making them vulnerable to arrest. About a dozen more have been jailed without trial or prevented from taking office by Mr. Maduro’s officials.

Elliott Abrams, the State Department’s special envoy for Venezuela, said other lawmakers have reported being offered hundreds of thousands of dollars to vote against Juan Guaidó, the leader of the National Assembly who faces internal re-election on Jan 5.

“What’s going on here is simple,” Mr. Abrams told reporters in Washington. “The regime is using a combination of threats, arrests and bribes — up to $500,000 per vote, we have been told — to stop the re-election of Juan Guaidó.”