W By Nick Anderson and Richard Simon

ASHINGTON – A much-delayed bill to create a new domestic security agency gained key congressional support Tuesday and appears all but certain to become law, a development that would hand President Bush a long-sought legislative victory.

As Congress returned for a lame-duck session, support for the president’s proposed Department of Homeland Security fell rapidly into place as key Democrats concluded they could no longer resist Bush in a dispute over the rights of government employees who would move into the agency.

House Republican leaders planned to force a vote as early as Wednesday on a final version of the bill that gives Bush most of the management powers he wanted, including the right to waive labor agreements when the president determines national security is at stake.

A key stumbling block in the bill’s approval has been whether the administration can waive civil service agreements in hiring and firing employees who would work in the new department.

The Senate was poised to act within days despite the misgivings of senior Democrats, as the erosion of opposition reflected Republican electoral gains. The GOP will maintain control of the House and take over the Senate in the next Congress.

“There is no doubt that the supporters of (Bush’s bill) are in a better negotiating position following the elections of last week,” Sens. Ben Nelson, D-Neb., John B. Breaux, D-La., and Lincoln Chafee, R-R.I., acknowledged in a joint statement.

The three centrists announced that they plan to vote for a slightly modified version of the Bush bill, giving the White House position a small majority. Most Republicans back the president on the issue; most Democrats oppose him.

Democrats could still mount a filibuster to block the bill, but an aide to Senate Majority Leader Tom Daschle, D-S.D., said such maneuvering was unlikely to succeed.

A filibuster could damage the re-election hopes of another Senate Democrat in a runoff election in Louisiana. Democrats do not want to force Sen. Mary L. Landrieu to explain a homeland security impasse as she campaigns in her Dec. 7 runoff against Republican challenger Suzanne Haik Terrell.

In addition to giving Bush a major legislative victory, the bill’s enactment would clear the way for a belated adjournment of the 107th Congress. Other legislation remains to be settled, including bankruptcy reform, terrorism insurance and annual government spending, but homeland security had been the predominant outstanding issue.

The bill would create a mammoth new Cabinet department, with roughly 170,000 employees drawn from 22 federal agencies. Thousands more workers could be heading into the department as the fast-growing federal aviation security force takes shape.

The final push came after months of stalemate. The House passed its first version in July with a large bipartisan majority, an action Bush praised. The bill then bogged down in the Democratic-led Senate as the two parties failed to reach agreement on worker rights. With White House support, GOP senators filibustered a Democratic version of the bill before the election.

After the Republicans gained enough seats in last week’s election to take full control of Congress, Bush pressed his advantage. He called for passage of the bill during the lame-duck session despite the initial suggestion from Senate Republican leaders that the bill be held over until next year.

Sen. Trent Lott, R-Miss., who will soon become majority leader, called Nelson on Friday night to begin negotiations. On Sunday, the staffs of Nelson, Breaux and Chafee met with the staffs of Lott and the White House. Lott then vetted the proposal with House GOP leaders. Afterward, the three centrists met and reluctantly agreed Tuesday to give their support.

Government unions denounced the labor-management provisions in the bill. They said Republicans had yielded little to their demands for a stronger union role in the new civil service rules and a stronger check on the president’s national-security waiver power.

“The modifications are so negligible as to be meaningless,” said Beth Moten, legislative director for the American Federation of Government Employees. She said the union would “strongly oppose” the bill. Colleen Kelley, president of the National Treasury Employees Union, also was opposed. Together, the two unions represent nearly 50,000 of the workers heading into the new department.

Many details of the final bill were not immediately known Tuesday night. But a 450-page draft circulating on Capitol Hill contained these provisions, according to congressional aides:

The secretary of the new department could revise civil service rules to give the president more latitude to hire, fire, demote and promote the workers he wants. If government unions object, they could seek changes and ask a federal mediator to step in. But the mediator’s recommendations would not be binding. The president could also waive collective bargaining rights of government employees if he notifies Congress that national security is in jeopardy.

The Bureau of Alcohol, Tobacco and Firearms – not previously affected by the legislation – would move from the Treasury Department to the Justice Department.

A Homeland Security Council would be established within the White House to coordinate domestic response to terrorist threats. It would be somewhat analogous to the National Security Council’s role in foreign affairs.

Airline pilots would be permitted to carry firearms as a last defense against hijackers. Also, there would be a potential extension of up to one year of a deadline for airports to ensure that all checked baggage is run through bomb-detection machines. The deadline is Dec. 31, but many airports are likely to fail to comply.

The bill, however, apparently omits a proposal to establish an independent commission to investigate the Sept. 11 attacks.

Bush met with Republican leaders and the new interim senator from Minnesota, independent Dean Barkley – who was sworn in Tuesday to fill out the term of the late Democrat Paul D. Wellstone – to push for final approval of his reorganization plan.

At its core, the department would be an anti-terror organization – spearheading defense of the nation’s borders, airports and seaports from sudden attacks. It would include the Coast Guard, the Customs Service, the Transportation Security Administration, the Federal Emergency Management Agency, the Secret Service, the Border Patrol and many other agencies.

It would be the third largest department, following Defense and Veterans Affairs.

Conceived in response to the Sept. 11 terrorist attacks, the department was first pushed by Democrats. Bush embraced the idea last June and then shaped it to his liking.