Glenn Greenwald, one of the journalists who broke the National Security Agency revelations from Edward Snowden in the Guardian, said on Sunday a book he is writing about the case will contain “a lot of new stories from the Snowden archive”.

Speaking to Brian Stelter, the host of CNN's Reliable Sources, at the end of a week in which Guardian US and the Washington Post shared a Pulitzer prize for public service reporting, Greenwald said: “There are stories that I felt from the beginning really needed the length of a book to be able to report and to do justice to, so there’s new documents, [and] there’s new revelations in the book that I think will help inform the debate even further.”

Greenwald left the Guardian in October 2013. In February 2014 he launched a website, The Intercept, which was the first venture from First Look, a media company backed by the eBay billionaire Pierre Omidyar. His book on Snowden is due out in May.

Greenwald, who lives in Brazil, recently returned to the US for the first time since stories about the NSA based on documents provided by Snowden were published, in June last year. On Friday 11 April he collected a George Polk Award, with Ewen MacAskill of the Guardian and the filmmaker Laura Poitras.

Asked about his return to the US and whether he had expected any government action, Greenwald said: “I had lawyers working for several months, including many who have connections at the highest levels of the Justice Department, trying to get some indication about what the government’s intentions were if I want to try to return. And they were given no information – they were completely stonewalled.



“The government wouldn’t say if there was a grand jury empaneled, if there was an indictment under seal, if they intended to arrest us. They wanted to keep us in this state of uncertainty.”

In August 2013 Greenwald's partner, David Miranda, was detained for nine hours at Heathrow airport, under UK terrorism laws.

Greenwald said the release of his book would likely lead to more visits back to the US.

“I think the material in the book which includes a lot of new stories from the Snowden archive has a lot of impact for the United States,” he said, “and I want to come back and talk to the people most affected by that story, which are Americans.”

On Monday, the Republican congressman Peter King used Twitter to say: “Awarding the Pulitzer to Snowden enablers is a disgrace.”

Asked about such opinions, which have also been expressed by figures within the Obama administration, Greenwald cited US government attitudes to previous cases involving whistleblowers, such as that of Daniel Ellsberg and the Pentagon Papers, and said: “You know, I look at Peter King’s condemnation as an enormous badge of honour.”