WASHINGTON -- The Department of Energy has fallen behind schedule to upgrade security at nuclear weapons sites, according to inspections at the Nevada Test Site and other properties outlined in a report issued Wednesday.

The test site had not completed all the upgrades scheduled for 2004 and for this year, such as new building designs to reduce potential vulnerabilities and train guards, and the hiring of additional guards, DOE inspector general auditors said.

In the meantime, the Nevada installation has increased its use of overtime by 39 percent to meet new requirements for an expanded guard force, according to the audit. An earlier report raised questions about "excessive overtime" by DOE guards.

Inspectors said they found similar conditions at other weapons sites run by the National Nuclear Security Administration, the DOE branch that manages the nuclear weapons complex.

Managers at the sites had suspended or reduced guard training and performance testing to ensure that personnel were available for mission duties, auditors said.

"It is critical that sites maintain momentum toward meeting the ... requirements in order to protect national security assets and operations," the 18-page report concluded.

As a result of delays, it said, the sites will have to implement, in one year, about 87 percent of the security plans to meet a schedule milestone of next October.

The complex is being given a growing role to safeguard nuclear materials transferred from weapons laboratories elsewhere.

Previous reports had described security lapses at the Nevada installation. An inspector general audit in February reported on two employees who brought unauthorized handguns onto the site.

Earlier, Energy Department officials acknowledged that security guards had performed poorly during a mock terrorist attack in August 2004.

The department is weighing a contract extension for longtime test site security contractor Wackenhut Services Inc.

Inspectors also visited the Sandia National Laboratories in New Mexico, the Pantex Plant in Texas and the Y-12 National Security Complex in Tennessee between August 2004 and August 2005.

The Office of Secure Transportation, which oversees nuclear materials shipping and has an operations center in Albuquerque, N.M., also was audited.

Glenn Podonsky, director of the DOE Office of Security and Safety Performance Assurance, agreed in a letter to Inspector General Gregory Friedman that progress was "slower than expected."

Another DOE official, Michael Kane, said the delays occurred because the security upgrade blueprints were not completed in time to be included in the department's budgets for 2004 and 2005.

In the aftermath of the Sept. 11, 2001, terrorist attacks, the Department of Energy updated its "design basis threat" requirements to defend sites where nuclear materials are stored, including the test site.

Security directors were told to incorporate new technologies into their operations, such as thermal imaging, laser detection, Doppler radar and remote sensing equipment.

Moves to install those items have been delayed, auditors said.