The man, alleged to have CIA ties, had help from three Venezuelan conspirators, who were arrested last week near a pair of oil refineries on the north Caribbean coast, Venezuela's Chief Prosecutor Tarek William Saab said on state television.
The office gave the U.S. suspect's name as Matthew John Heath.
The prosecutor showed pictures of equipment allegedly seized from the group, including a grenade launcher, plastic explosives, a satellite phone and a bag of U.S. dollars. Authorities said cellphones taken from the men when they were arrested last week include images of a large bridge in Zulia state and dilapidated oil refineries in Falcon state.
“Everything here could qualifies as a lethal weapon designed to cause harm and to promote assassinations, crimes against the people of Venezuela,” said Saab, who also accused the man of planning to open a drug trafficking route through Venezuela.
President Nicolás Maduro announced on Friday that an unnamed suspected U.S. spy had been captured, saying he was a Marine and former CIA operative in Iraq.
U.S. authorities have not commented on the case. The Associated Press was unable to make immediate contact with Heath, an attorney or a relative representing him for comment on the accusations.
The arrest surfaced as this nation, once wealthy from oil, has been gripped by a deep gasoline shortage that has sparked mile-long lines to fuel up, even in the capital of Caracas. Venezuela also struggles to provide electricity to residents, especially in Zulia state, once a major hub of the nation's vast oil production.
Heath is accused of entering Venezuela illegally, the prosecutor said, adding that he didn't have a passport but rather had a copy of it hidden in one of his shoes. The three Venezuelans accused of conspiring with Heath include a military officer, Saab said, adding that they helped him enter from Colombia.
Saab said Heath had worked as a mercenary in Iraq from 2006 to 2016 for MVM Inc., a Virginia-based private security contracting company. The firm did not immediately respond to phone and email messages seeking comment.
Heath has been charged with terrorism, trafficking illegal weapons and conspiracy, authorities said.
The arrest follows a failed beach incursion in early May that landed two ex-Green Beret soldiers in a Venezuelan jail for allegedly participating in a failed attempt to overthrow the socialist government.
The two former U.S. special forces soldiers were arrested along with more than 80 rebel Venezuelan fighters who staged a failed beach attack called Operation Gideon aimed at arresting Maduro.
The operation mounted from makeshift training camps in neighboring Colombia left several rebels dead. It was orchestrated by Jordan Goudreau, an American citizen and three-time Bronze Star recipient who served in Iraq and Afghanistan.
The ex-Green Berets in Goudreau's force — Luke Denman Airan Berry Venezuela — have been sentenced to 20 years in prison. Authorities say the two men confessed to being part of the plot.
While the Trump administration denied having anything to do with the bungled May incursion, Washington backs Venezuelan opposition politician Juan Guaidó as the country's legitimate leader in place of Maduro.
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