Venezuela's state TV has shown a video of a US citizen apparently confessing to plotting to overthrow President Nicolás Maduro and bring him to the US.
Luke Denman is one of 13 people arrested over the weekend. Venezuela says they are "mercenaries" whose armed incursion was foiled.
Mr Maduro has often accused US President Donald Trump of trying to invade the country and overthrow him.
Mr Trump earlier this week denied any US involvement.
Secretary of State Mike Pompeo has said the US government will use "every tool" to secure the return of the Americans.
