The United States had been considering a coup to overthrow the elected Venezuelan president, Hugo Chavez, since last June, a former US intelligence officer claimed yesterday.
It is also alleged that the US navy aided the abortive coup which took place in Venezuela on April 11 with intelligence from its vessels in the Caribbean. Evidence is also emerging of US financial backing for key participants in the coup.
Both sides in Venezuela have blamed the other for the violence surrounding the coup.
Wayne Madsen, a former intelligence officer with the US navy, told the Guardian yesterday that American military attaches had been in touch with members of the Venezuelan military to examine the possibility of a coup.
"I first heard of Lieutenant Colonel James Rogers [the assistant military attache now based at the US embassy in Caracas ] going down there last June to set the ground," Mr Madsen, an intelligence analyst, said yesterday. "Some of our counter-narcotics agents were also involved."
He said that the navy was in the area for operations unconnected to the coup, but that he understood they had assisted with signals intelligence as the coup was played out.
Mr Madsen also said that the navy helped with communications jamming support to the Venezuelan military, focusing on communications to and from the diplomatic missions in Caracas belonging to Cuba, Libya, Iran and Iraq - the four countries which had expressed support for Mr Chavez.
Navy vessels on a training exercise in the area were supposedly put on stand-by in case evacuation of US citizens in Venezuela was required.
In Caracas, a congressman has accused the US ambassador to Venezuela, Charles Shapiro, and two US embassy military attaches of involvement in the coup.
Roger Rondon claimed that the military officers, whom he named as (James) Rogers and (Ronald) MacCammon, had been at the Fuerte Tiuna military headquarters with the coup leaders during the night of April 11-12.
And referring to Mr Shapiro, Mr Rondon said: "We saw him leaving Miraflores palace, all smiles and embraces, with the dictator Pedro Carmona Estanga [who was installed by the military for a day] ... [His] satisfaction was obvious. Shapiro's participation in the coup d'état in Venezuela is evident."
The US embassy dismissed the allegations as "ridiculous". Mr Shapiro admitted meeting Mr Carmona the day after the coup, but said he urged him to restore the national assembly, which had been dissolved.
Mr Carmona told the Guardian that no such advice was given, although he agreed that a meeting took place.
A US embassy spokesman said there were no US military personnel from the embassy at Fuerte Tiuna during the crucial periods from April 11 to 13, al though two members of the embassy's defence attache's office, one of them Lt Col Rogers, drove around the base on the afternoon of April 11 to check reports that it was closed.
Mr Rondon has also claimed that two foreign gunmen, one American and the other Salvadorean, were detained by security police during the anti-Chavez protest on April 11 in which around 19 people were killed, many by unidentified snipers firing from rooftops.
"They haven't appeared anywhere. We presume these two gentlemen were given some kind of safe-conduct and could have left the country," he said.
The members of the military who coordinated the coup have claimed that they did so because they feared that Mr Chavez was intending to attack the civilian protesters who opposed him.
Mr Chavez's opponents claim pro-Chavez gunmen shot protesters while his supporters say the shots were fired by agents provocateurs .
In the past year, the United States has channeled hundreds of thousands of dollars in grants to US and Venezuelan groups opposed to Mr Chavez, including the labour group whose protests sparked off the coup. The funds were provided by the National Endowment for Democracy, a nonprofit agency created and financed by the US Congress.
The state department's human rights bureau is now examining whether one or more recipients of the money may have actively plotted against Mr Chavez.