The White House is taking new steps to safeguard classified information and protect government computer networks against unauthorised disclosures such as last year's release of thousands of pages of secret documents by the website WikiLeaks.

An executive order signed on Friday by President Barack Obama is the result of a seven-month review by his administration.

It sought to find a proper balance between security and the need for agencies to share classified information, one of weaknesses revealed by the September 11, 2001, terrorist attacks.

Under the order, the government will create a special committee to coordinate information sharing and to ensure that agencies that use classified computer networks protect information.

Each agency will have a senior official oversee classified information and be responsible for safety measures.

Departments and agencies, including the Pentagon and the Central Intelligence Agency, have already taken steps to control people's ability to place classified data on disks or removable memory devices and have limited the number of users with permission to use such devices.

"Our nation's security requires classified information to be shared immediately with authorised users around the world but also requires sophisticated and vigilant means to ensure it is shared securely," Obama's order says.

The order instructs Attorney General Eric Holder and the U.S. director of national intelligence, James Clapper, to establish an "Insider Threat Task Force" to find ways to deter and detect security breaches.