Media experts say there is no evidence that any of the reporting endangered national security, and Greenwald, Poitras and MacAskill have emphasized how carefully they treated the material.

Their supporters say it would be damaging for the credibility of the Pultizer Board, which has a reputation for being conservative, not to honor the biggest scoop in a decade.

"They would have surrendered to the right wing or the culturally conservative on security questions in American politics," said Christopher Simpson, communications professor at American University in Washington.

The US media is considered more conservative on questions of US national security than foreign publications.

About the broadcaster:

Anne Ruisi is an editor at China Daily online with more than 30 years of experience as a newspaper editor and reporter. She has worked at newspapers in the U.S., including The Birmingham News in Alabama and City Newspaper of Rochester, N.Y.

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