The New York Times newspaper has sought a court order to block federal investigators from obtaining records of telephone calls made by two of its reporters after the 11 September 2001 attacks.
The US Department of Justice is subpoenaing the records from telephone companies as part of an investigation into whether government officials tipped off the reporters about investigations of Islamic charities.
But the newspaper says the records would reveal the identities of dozens of confidential sources who provided information for articles about the attacks on the Pentagon and the World Trade Centre.
The newspaper says its news-gathering abilities would be severely impaired if the government could obtain records of communications between reporters and their sources.
Carl Bernstein, one of the two reporters who broke the Watergate scandal in the US which led to president Richard Nixon's resignation in 1974, said government intrusion into the relationship between reporters and their sources would erode press freedom.
