Bush signed a directive last July ordering the government to develop, for the first time, rules for deciding when and how the United States would penetrate and disrupt foreign computer systems, the newspaper said.

The secret national security directive had not been publicly disclosed until now, the newspaper reported.

According to the report, cyber-warfare rules were being prepared amid speculation that the Pentagon was considering some offensive computer operations against Iraq if the president decides to go to war over Baghdad's banned weapons programs.

"Whatever might happen in Iraq, you can be assured that all the appropriate approval mechanisms for cyber-operations would be followed," an administration official was quoted as saying. The official declined to confirm or deny whether such planning was underway, the newspaper said.

A White House spokesman was not immediately available for comment.

The Post cited unnamed senior officials as saying that the United States has never conducted a large-scale, strategic cyber-attack, but the Pentagon has stepped up development of cyber-weapons.

Military planners imagine soldiers at computer terminals silently invading foreign networks to shut down radars, disable electrical facilities and disrupt phone services, the newspaper said.

Despite months of discussions involving the Pentagon, CIA, FBI and National Security Agency, officials told the paper a number of cyber-warfare issues remain to be resolved and that the president's directive was just an initial step.

A senior administration official told the newspaper: "We're trying to be thorough and thoughtful about this. I expect the process will end in another directive ... setting the foundation."