Yet he also was feeding information to the communist-led revolutionary forces.

The intelligence he provided was so accurate and detailed that General Vo Nguyen Giap reportedly said, We are in the US operations room," as he was reading it.

At the same time he worked for British news agency Reuters and Time magazine.

It was a huge surprise to his former colleagues when, in the 1980s, he announced his true allegiance.

During the 1960s and '70s he was one of the most influential journalists working in Vietnam.

His network of contacts gave him access to almost every part of the government and military of the former American-backed regime.

He said he never reported any false information in all the years he worked as a journalist.

Although he had studied in the US and had a great respect for the country, he said working for the communists had been the only way to ensure Vietnam's independence.

A chain-smoker, An died of emphysema in hospital in Ho Chi Minh City in 2006.