President Bush, who has made national security the centerpiece of his campaign for re-election, has signed an order designed to improve the nation's defenses against bioterror attacks (search).

The presidential directive, which Bush signed last week, attempts to plug gaps in the nation's biodefenses, an administration official said on condition of anonymity.

An unclassified version of the directive was being released at a briefing Wednesday.

The directive works to coordinate what the government already is doing to protect food and water supplies, for example.

The Bush administration would not release the directive on Tuesday, but memos posted on the Web site of the Association of Metropolitan Water Agencies (search) said the directive "has a strong emphasis on the water sector."

For more on the campaign, click to view Foxnews.com's You Decide 2004 page.

One memo said the directive's general concept for protecting water is a surveillance system for water supplies that would be similar to an early-warning system designed to detect intentional releases of harmful biological materials.

The new directive orders the Environmental Protection Agency (search) to develop a plan to examine how such a surveillance system could be set up to protect the nation's water supply, the memo said.

Administration officials worked for months to identify holes in the nation's defense against biological attacks and find ways to fix them. The effort was led by retired Gen. John Gordon, Bush's homeland security adviser, who took a broad look at the problems, focusing on threats that were considered the most likely to happen.

Democrats on the House Homeland Security Committee accused the administration of not moving fast enough to help prevent biological attacks. Moira Whelan, a spokeswoman for the committee's Democrats, said Tuesday night they had seen neither version of the directive.

In a report released in late February on the one-year anniversary of the creation of the Homeland Security Department, the Democrats were critical of the pace of the administration's efforts to improve protection in the country from bioterrorism. "The administration has not responded to this threat as aggressively or as comprehensively as is needed, leaving foreign and domestic stores of deadly pathogens unsecured," the report said.

A comprehensive plan, the report said, would include securing stocks of biological agents around the world; boosting and targeting federal public health money and deploying drugs, vaccines and other equipment throughout the nation to combat possible infection and illness.