Just hours ahead of an expected release of three million classified U.S. documents, the website WikiLeaks said it has been the target of a computer attack.

“We are currently under a mass distributed denial of service attack,” WikiLeaks tweeted midday Sunday.

Fifteen minutes later, WikiLeaks vowed that it would go ahead with the document dump, which is expected to include State Department cables that Washington fears will wound foreign relations, through its media partners, who received advance access to the documents, if they couldn’t get the site back up in time.

“El Pais, Le Monde, Speigel, Guardian & NYT will publish many US embassy cables tonight, even if WikiLeaks goes down,” WikiLeaks tweeted.

The Guardian site was also briefly down Sunday morning with a 404 error.

The State Department’s top legal adviser, Harold Koh, made a last-ditch effort to stop the documents’ release in a Saturday letter to WikiLeaks founder and spokesman Julian Assange, saying that the release would “place at risk the lives of countless innocent individuals — from
journalists to human rights activists and bloggers to soldiers to
individual providing information.”

“At a minimum,” he wrote, the release would also “place at risk” ongoing military operations and foreign cooperation.

Koh stressed that the administration would not negotiate with Assange in his request to know which individuals would be harmed.

”Despite your stated desire to protect those lives, you have done the opposite and endangered the lives of countless individuals,” Koh said in underline. “You have undermined your stated objective by disseminating this material widely, without redaction, and without regard to the security and sanctity of the lives your actions endanger.”