Pentagon officials announced yesterday that they soon will begin implementing a controversial personnel system that they believe can withstand the kind of legal challenge that has hampered a similar plan at the Department of Homeland Security.

The National Security Personnel System, which eventually will cover 650,000 civilian employees, will replace the familiar 15-grade General Schedule pay system with one in which raises are linked to annual performance evaluations.

The new work rules also would curtail the power of labor unions and make it easier to hire, promote and discipline employees -- all in the name of making the Defense Department more nimble in the struggle against terrorism.

The new system gives the federal government's largest department "the opportunity to provide an environment for our people to excel, to be challenged and to be rewarded," Gordon R. England, the acting deputy secretary of defense, said in a briefing for reporters yesterday.

"I continue to believe the vast majority of our people will embrace NSPS because of the opportunities it provides them and the challenges they will have," he added.

The early reviews are not so favorable. At least five federal employee unions, led by the American Federation of Government Employees, say they will file a lawsuit in federal court to challenge the labor relations portions of the new system.

The unions contend that the new work rules would gut collective bargaining in violation of federal law. And they maintain that the department did not live up to its obligation to consult with employees' representatives in developing a new labor management system.

A similar lawsuit against Homeland Security has effectively delayed the implementation of a new pay system there by as much as a year.

In August, U.S. District Judge Rosemary M. Collyer faulted the new DHS system for undermining employees' rights to collective bargaining, and blocked implementation of new rules governing labor relations and employee appeals. DHS has not said whether it will appeal.

Mark Roth, AFGE's general counsel, said the Pentagon's new system is similarly flawed. "They've done a lot of the same things in these regs that Judge Collyer found illegal in our DHS lawsuit," he said. "They've changed the terminology, but it's still the same substance."

The department will publish the new work rules in the Federal Register today, triggering a 30-day congressional review period. Pentagon officials hope to implement the labor relations portions -- including a new internal labor relations board controlled by the defense secretary to resolve labor management disputes -- department-wide immediately after that.

Pay raises for 2006 would be awarded according to the current system. About 113,000 employees would move to the new pay system by April, with all of them having to go through the new annual performance evaluations for at least a portion of their raises in 2007.

An additional 160,000 workers would move to the new pay system late next year but would not see their raises affected until 2008. The remaining 377,000 employees would join the system later.

By law, no worker's salary can be decreased in the move to the new system.

Bush administration officials have said that elements of the new systems at both DHS and Defense could serve as guides for government-wide changes in civil service rules.

"All of us through the government are watching how this goes," Linda Springer, head of the Office of Personnel Management, said at yesterday's briefing. "There's a lot at stake."

England and other administration officials noted that union contracts can already be overridden in some circumstances. They also said their plan can withstand a lawsuit because it was devised under a different law than the one that allowed DHS to rewrite its personnel rules.

"We have a different program, a different law," England said. "And I believe that we have met the spirit and the intent of what the Congress wanted us to do. This is a very balanced program. It provides all the protections."

Roth, the AFGE official, disagreed.

"We're just very disappointed. We have a lot of interests in common -- good management, fast decisions, effective decisions," he said. "We think it's doomed to failure. We don't think these regulations are going to lead to a better system."

Staff writers Stephen Barr and Eric Yoder contributed to this report.

Gordon R. England, the acting deputy secretary of defense, said most Defense Department workers will support the National Security Personnel System.