Washington ? The Senate kicked off a contentious debate Tuesday on President Bush’s blueprint for a Homeland Security Department, with Democrats flatly rejecting White House demands for greater management flexibility over the agency’s estimated 170,000 employees.

The White House responded with a statement repeating Bush’s vow to veto the Senate measure, largely over the worker dispute.

Senate Majority Leader Tom Daschle called Bush’s proposal “a power grab of unprecedented magnitude” that would undermine the nonpolitical government civil service system and threaten labor union rights and protections for one-third of the workers.

“We’re not going to roll over when it comes to principles and beliefs we hold to be very, very important,” said Daschle, D-S.D.

The White House and its Republican congressional allies also dug in their heels. Tom Ridge, the president’s point man on homeland security, said the new department needed broader powers to hire, fire, promote or demote and pay employees and waive union rights in matters of national security to meet emerging terrorist threats.

“The president has indicated it’s not just a matter of reconfiguring letterheads and addresses,” Ridge said after meeting privately with Republican senators.

The Senate GOP leader, Trent Lott of Mississippi, predicted Bush would bring enough political pressure to bear to get much of what he wants in the end.

“It’s about doing the job. If we get into this political folderol I think that’s a mistake,” Lott said.

The president met Tuesday with GOP senators at the White House to reinforce his demands for the new Cabinet agency and planned similar sessions later this week with Democrats.

“I don’t recall the term veto being used by the president, but he made it very clear that the bill had to be acceptable to him, that he wasn’t going to accept some these are my words weak compromise,” Sen. Bob Smith, R-N.H., told reporters afterward.

Later in the day, however, the White House issued a statement stating that Bush would veto the Senate bill “in its current form.” In addition to the personnel issues, the statement said Bush objects to the bill’s “intrusive” new White House Homeland Security Office with a Senate-confirmed director.

As the battle lines hardened, the Senate voted 94-0 to proceed to full debate, which could take two or three weeks.

Presidential power to waive union collective bargaining rights for federal employees for national security reasons has existed since 1977, said Sen. Fred Thompson, R-Tenn. Congress has approved more flexible personnel systems for agencies such as the Internal Revenue Service, the Department of Housing and Urban Development, the Federal Aviation Administration and the new Transportation Security Administration.

Even though there was no immediate sign of compromise on the personnel dispute, both sides predicted the Senate would pass a Homeland Security bill later this month. That would set up negotiations on a final version with the House, which in July approved a measure much like Bush’s original plan.

Both bills would merge all or parts of 22 agencies into a single department focused on protecting Americans against terrorism at home. The Coast Guard, Transportation Security Administration, Customs Service, Border Patrol, Secret Service and Federal Emergency Management Agency are among those to be moved.

Both measures also would set up a new intelligence analysis office the Senate’s version is more powerful that would sift through data produced by the CIA, FBI and others to identify potential threats and take action to protect targets or prevent terrorist acts.