(CNN) -- The U.S. Air Force defended its decision to cut off access to WikiLeaks and news organizations that published the same classified documents Wednesday despite criticism of what one observer called a "pointless" move.
The White House Office of Management and Budget has already forbidden federal employees and contractors from accessing classified documents publicly available on WikiLeaks and other websites via computers or mobile devices. But the Air Force has cut off access to over 25 sites, including WikiLeaks and three newspapers that have worked with the site to release a cache of U.S. diplomatic cables -- The New York Times, The Guardian in Britain and Germany's Der Spiegel.
Those three have been singled out because they are posting the documents directly, rather than simply reporting on their content, as other news organizations -- including CNN -- have done, said Maj. Toni Tones, an Air Force spokeswoman.
The Air Force is the only one of the armed services to take those steps, Tones said. She said the Air Force is trying to prevent classified material from making it onto unclassified systems, which she said would force its personnel to waste time and money chasing them down and removing them.
"Our actions to block the access of classified material from an unclassified network is not to discriminate against any news outlet or information website," she said. "The primary purpose is to ensure the security of our unclassified systems and to safeguard classified information."
WikiLeaks, which facilitates the disclosure of secret information, began releasing a cache of more than 250,000 U.S. diplomatic cables from around the world in November. The site previously released hundreds of thousands of military documents from the wars in Iraq and Afghanistan.
The Air Force move comes after several widely publicized warnings by federal agencies and some prestigious colleges that reading the classified documents released by WikiLeaks could endanger job prospects. And since more than 2,000 supporters have set up "mirror" sites that post the documents WikiLeaks is releasing, critics say there's no logic in barring access to documents that are now publicly accessible.
"It's been so widely reported, it can't be that we're trying to keep them from seeing this information," said Fran Townsend, a former White House homeland security adviser and a CNN contributor.
And CNN legal analyst Jeffrey Toobin called the policy "a rather pointless protest."
"Our enemies can see the documents, but not those whom we trust to defend our country," he said.
But Tones said the policy will stand "until we feel that the sites don't pose a threat to our unclassified systems."
A U.S. Army intelligence specialist, Pfc. Bradley Manning, is suspected of releasing the documents to WikiLeaks. Manning is currently awaiting trial on charges of illegally downloading classified material and providing video of a 2007 helicopter attack in Iraq to WikiLeaks.
The Air Force has not yet taken any action against anyone for violating its policy, she said.