Glenn Greenwald, the lawyer and blogger who brought The Guardian the biggest scoop of the decade, is departing the London-based news organization, for a brand-new, large-scale, broadly focused media outlet, he told BuzzFeed Tuesday.

Greenwald, 46, published revelations from former National Security Agency contractor Edward Snowden about the extent of American and British domestic spying and about officials' deception about its scope. He said he is departing for a new, "once-in-a-career dream journalistic opportunity" with major financial backing, the details of which will be public soon.

"My partnership with The Guardian has been extremely fruitful and fulfilling: I have high regard for the editors and journalists with whom I worked and am incredibly proud of what we achieved," Greenwald said in an emailed statement. "The decision to leave was not an easy one, but I was presented with a once-in-a-career dream journalistic opportunity that no journalist could possibly decline."

Greenwald said that because the news had leaked "before we were prepared to announce it, I'm not yet able to provide any details of this momentous new venture." It will, he said, "be unveiled very shortly."

A Guardian spokeswoman, Jennifer Lindenauer, also stressed that the writer and his news organization are parting on good terms — though she said The Guardian is "disappointed" to lose him.

"Glenn Greenwald is a remarkable journalist and it has been fantastic working with him," Lindenauer said in an email. "Our work together over the last year has demonstrated the crucial role that responsible investigative journalism can play in holding those in power to account. We are of course disappointed by Glenn's decision to move on, but can appreciate the attraction of the new role he has been offered. We wish him all the best."

The Guardian, with a tradition of rigorous, crusading, liberal reporting and experience with two extremely sensitive international investigative stories — WikiLeaks and the News Corp. phone-tapping scandals — was in some ways a perfect home for Greenwald's reporting, which in turn offered a huge boost to The Guardian's American and global prestige.

But Greenwald never functioned as a typical employee of a news organization. He told BuzzFeed in August that he had not shared all of Snowden's files with The Guardian, and that "only [filmmaker] Laura [Poitras] and I have access to the full set of documents which Snowden provided to journalists." The Guardian, facing intense pressure from the British government, has continued to publish Snowden's revelations at a deliberate pace in recent weeks; but Greenwald has moved more quickly on his own, publishing stories in Brazil and India. He said recently that he will also publish stories soon in Le Monde.

Greenwald declined to comment on the precise scale of the new venture or on its budget, but he said it would be "a very well-funded … very substantial new media outlet." He said the source of funding will be public when the venture is officially announced.

Politico reported later Tuesday that a "philanthropist" would fund the venture. A spokesman for George Soros, perhaps the most famous philanthropist of the American left, ruled Soros out as the backer. "They have had no contact," Soros spokesman Michael Vachon said of Greenwald.

"My role, aside from reporting and writing for it, is to create the entire journalism unit from the ground up by recruiting the journalists and editors who share the same journalistic ethos and shaping the whole thing — but especially the political journalism part — in the image of the journalism I respect most," he said.

Greenwald will continue to live in Rio de Janeiro, Brazil, he said, and would bring some staff to Rio, but the new organization's main hubs will be New York City; Washington, D.C.; and San Francisco, he said.

The venture, which he said had "hired a fair number of people already," will be "a general media outlet and news site — it's going to have sports and entertainment and features. I'm working on the whole thing but the political journalism unit is my focus."

Greenwald said he looked forward to creating a new organization with "no preexisting institutional strictures on what you can do."

And he said his move is driven solely by the opportunity presented.

"When people hear what it is, there is almost no journalist who would say no to it," he said.