Among the 16,000 documents is a CIA memorandum confirming US funded attempts to undermine the democratically elected Marxist president, Salvador Allende, who was overthrown in a bloody coup in 1973.

The US funded opponents of President Allende

A researcher at the National Security Archive in Washington Peter Kornbluh, told the BBC he thought the documents would re-write America's role in Chile.

Earlier records showed that the US turned a blind eye to political repression against opponents of the military ruler, General Augusto Pinochet, who came to power in the coup.

"Actions approved by the US Government during this period aggravated political polarisation and affected Chile's long tradition of democratic elections and respect for constitutional order and the rule of law," a White House statement said on Monday.

Covert aid

It is the third and final batch of CIA records to be released on the period of military rule in Chile, following a review ordered by President Clinton.

The release was ordered in 1999, to allow the public to "judge for itself the extent to which US actions undercut the cause of democracy and human rights in Chile".

Thousands died and disappeared during General Pinochet's rule

The records show that just three weeks before President Allende was toppled, US officials had approved $1m in covert aid to political parties and private organisations.

The records also detail a long history of covert anti-Allende efforts, including actions aimed at preventing him from taking office, destabilising his government once he was in office, and helping General Pinochet consolidate his power.

State-sponsored terrorism

Washington has long denied accusations that it played a direct role in the coup.

Thousands of people died or disappeared during General Pinochet's rule

One important document shows that General Pinochet once asked his Paraguayan counterpart for false passports for Chilean agents travelling to the United States.

The BBC's correspondent in Santiago, James Reynolds, says some people in Chile believe this could be used as evidence against General Pinochet, to show that he ordered the 1976 assassination of former foreign minister, Orlando Letelier, who was killed in a car bomb attack in Washington DC.

One of the men convicted in 1993 for his role in the assassination was a paid informant for the CIA, according to documents recently released by the Pentagon's Defence Intelligence Agency.

The man, Manuel Contreras, was the former head of of the secret police in Chile and one of the most feared men in Chile, second only to General Pinochet.

The documents show that contact between the CIA and Mr Contreras - General Pinochet's closest friend and confidant - began in 1974.

The assassination, in which a colleague of Mr Letelier also died, has been described as one of the worst cases of state-sponsored terrorism in the US.

General Pinochet's iron rule was underpinned by the tactics of brutal repression that saw thousands die and thousands more flee into exile. Others disappeared or were tortured.