"If the Maduro regime decides to hold them, we will use every tool that we have available to try to get them back," Pompeo told reporters.

He reiterated President Donald Trump's denial of US involvement, quipping: "If we had been involved, it would have gone differently."

Venezuelan President Nicolas Maduro, whom the United States has been seeking to topple for more than a year, on Monday displayed the passports of two Americans he said were arrested in a plot to bring him down.

While it was unclear where they were detained, Venezuelan officials earlier said they had foiled an attempted landing by mercenaries on a beach near Caracas in which eight people were killed.

Maduro tried to tie the alleged plot to Juan Guaido -- the opposition leader considered interim president by the United States and some 60 other countries.

Venezuelan officials said that Guaido had a $212 million contract with a Florida-based security firm founded by former US special forces soldier Jordan Goudreau, who has openly said he is working to oust Maduro.

Guaido denied the contract and Pompeo declined comment.

"As for who bank-rolled it, we're not prepared to share any more information about what we know," Pompeo said.

The State Department earlier dismissed Maduro's account as "melodrama" and accused him of concocting details to deflect from mounting troubles at home.