Senate Democrats and Republicans remained at an impasse Thursday over worker rights in the proposed Homeland Security Department as President Bush endorsed a new alternative.

In a 50-49 test vote along party lines, the Senate fell short of the 60 votes needed to prevent major GOP changes to a Democratic version of the bill. Bush has threatened to veto that version because it does not give him broad authority he seeks to rapidly hire, fire and deploy the agency's 170,000 workers to respond to terrorist threats.

A few hours after the vote, Bush endorsed an alternative being circulated by Sens. Phil Gramm, R-Texas, and Zell Miller, D-Ga., that makes some modest concessions to Democrats on the crucial issues of civil service and union protections.

Bush said the Gramm-Miller version is a "comprehensive substitute for a piece of legislation which we believe is flawed." After touring a White House homeland security facility, Bush said the Senate must act in time for Congress to pass an acceptable bill before adjourning for the year.

"We're at a time of war and the Senate shouldn't be making it harder for an administration, whether this one or future administrations, to do their job," Bush told reporters. "America is still threatened. There are enemies out there which still hate us."

After quick House action in July, the Senate is in its third week of sluggish debate on Bush's plan to combine 22 agencies into a single department focused on protecting Americans from terrorism at home. The Coast Guard, Border Patrol, Customs Service, Transportation Security Administration and Secret Service are among those that would be transferred.

Although far from conclusive, the Senate vote Thursday ensured that Republicans will be able to offer amendments giving Bush the personnel powers he seeks. Democrats adamantly oppose those powers as attacks on the civil service system and union bargaining rights.

"I will fight that with every bone in my body," said Sen. Barbara Boxer, D-Calif.

Yet Miller, a conservative who frequently breaks with Democratic leaders, said there are others in his party willing to back the alternative. He predicted many Democrats, facing a November election with control of Congress at stake, would eventually vote for a Homeland Security Department similar to that sought by Bush despite the influence wielded by labor unions within the party.

"We are not doing our party any good by feeding the perception that Democrats are undermining the president of the United States on the war on terrorism," Miller said. "It's just been one long negative ad for the other side, free of charge."

The Gramm-Miller proposal would preserve the president's existing power to exempt workers from union coverage for reasons of national security, but would add requirements for advance, written notification of employees and Congress that union rights were being withdrawn.

The measure also includes a House-passed provision allowing the creation of a new personnel system within the department but guarantees certain basic protections, such as those prohibiting discrimination and protecting whistle-blowers who disclose waste and wrongdoing.

It would make 15 other changes to the Democratic bill, creating a less powerful intelligence function but blocking Bush's request for the ability to shift up to 5 percent of the agency's budget without congressional approval.

Gramm acknowledged the proposal does not yet command a Senate majority but said the issue will come to a head next week.

"If we don't do this before the election, we deserve the righteous contempt of the American people," he said.

Democratic leaders initially held their fire on the new proposal. Majority Leader Tom Daschle, D-S.D., said "we don't know" if the measure would gain significant Democratic support because the details were still emerging.

Daschle did say, however, that the GOP vote against the Democratic bill "would speak volumes about the Republicans' intransigence on homeland security."

Also Thursday, Sens. Joseph Lieberman, D-Conn., and John McCain, R-Ariz., introduced an amendment that would set up an independent commission to investigate intelligence failures prior to the Sept. 11 terror attacks. A vote on that measure was not expected until next week.

Bush also kept in place a declaration of national emergency that served as the legal basis for his efforts to block assets of terrorists and those who support them.

The administration is required to renew the declaration periodically. In a report to Congress, the White House reported it had blocked $75,000 in assets belonging to groups or people tied to terrorism.