The Pentagon yesterday condemned the latest release of classified documents by the website WikiLeaks and unveiled steps designed to prevent future disclosures of secret files.

“As we have in the past, we condemn this reckless disclosure of classified information illegally obtained,” Pentagon spokesman Bryan Whitman said in a statement.

As WikiLeaks released 250,000 diplomatic cables to The New York Times yesterday, the Defense Department announced a series of measures undertaken in recent months to “prevent further compromise of sensitive data.”

The steps were taken after Pentagon reviews launched in August that followed the disclosure of tens of thousands of US military intelligence files on the war in Afghanistan.

The measures included disabling all write capability for thumb drives or removable media on classified computers, restricting transfers of information from classified to unclassified systems and better monitoring of suspicious computer activity using similar tactics employed by credit card companies, Mr Whitman said.

“Bottom line: It is now much more difficult for a determined actor to get access to and move information outside of authorized channels,” Mr Whitman said.

Late on Saturday Washington ruled out negotiating with WikiLeaks, saying it possessed the cables in violation of US law.

US officials said this was in response to a letter Mr Assange had sent to the State Department on Friday in which he had tried to address concerns that the planned release placed individuals at risk.

“As far as we are aware, and as far as anyone has ever alleged in any credible manner whatsoever, no single individual has ever come to harm as a result of anything that we have ever published,” Mr Assange said.