Nicolas Maduro said the plan was to blame his opponent’s murder on the OPEC nation’s government and to “fill Venezuelans with hate” as they prepare to vote following the death of socialist leader Hugo Chavez.

The United States denied the claim. “We categorically reject allegations of US government involvement in any plot to harm anyone in Venezuela,” State Department spokesman Patrick Ventrell said.

Mr Maduro, a 50-year-old former bus driver and union leader, first mentioned a plot against his rival, Henrique Capriles, last week. He blamed it on former Bush administration officials Roger Noriega and Otto Reich. Both rejected the allegations as untrue, outrageous and defamatory.