An 11th-hour effort to secure a new tax for Northern Virginia's Metro system collapsed tonight giving the Virginia General Assembly one day to resolve two key issues that have evaded solution throughout an acrimonious 60-day session.

Although the legislators killed one Metro tax measure tonight and filibustered against another, legislators were to return to the State Capitol Saturday for a final attempt at both Metro financing and replenishing the state's dwindling highway fund.

If they fail, governments in Washington's Virginia suburbs will be forced to continue financing the increasingly expensive transit system largely with local property taxes and the state government might have to curtail its highway construction program.

Today's dramatic and chaotic legislative events were set in motion when Northern Virginia's eight senators, fearful of voter anger over the size of the 4 percent regional gasoline tax they had previously supported, abruptly abandoned that proposal for a 1 percent increase in the sales tax on food, clothing and most other retail goods.

While the new sales tax proposal breezed through the state Senate by a 37-to-2 vote this afternoon, it died a few hours later in the House Finance Committee by 11-to-9.

Opponents then successfully filibustered for 90 minutes on the Senate floor to prevent the Senate Finance Committee from meeting tonight to approve the Northern Virginias' original bill for a 4 percent regional gasoline levy. The House of Delegates has already approved that proposal.

The opponents' objective was to hold any form of Metro funding hostage until the Northern Virginians agreed to help scuttle the Dalton gasoline increase. Area lawmakers said tonight they would hold to a previous commitment to back the Dalton plan.

'We finally convinced them (the opponents) that we were going to honor our commitment to vote for the statewide gasoline tax no matter what," said Sen. Joseph V. Gartland (D-Fairfax) after the filibuster ended. He added that doubt about commitment had prompted opponents to attempt their hostage strategy.

Gartlan said he was optimistic that some form of Metro funding -- probably a scaled-down version of the 4 percent tax -- would pass Saturday. But other area legislators, stunned and grim-famed after tonight's setbacks, said they may decide to scrap the regional tax proposal altogeher and force Northern Virginia localities to allocate part of their own tax resources for the multibillion-dollar rail and bus system.

The filibuster -- the Senate's first in four years -- began unexpectedly at 7:30 p.m. when Norfolk Democrat Pete K. Babalas rose on a point of "personal privilege."

Babalas, an adamant foe of the Dalton tax, then monopolized the floor, refusing to yield, reading from sections of the Virginia Code. He was spelled by other opponents, who planned to go as late as necessary to prevent the Senate Finance Committee from meeting to approve the regional gasoline tax bill. Under Senate rules, most committees, including Finance, cannot meet unless the Senate is adjourned or in recess.

By delaying the Finance Committee session until Saturday, the opponents hoped to set up a situation in which the Northern Virginians would need to muster 32 votes -- four-fifths of the senators -- to take up consideration of the Metro bill before adjournment Saturday night.

So the opponents droned on. As some senators ate hamburgers and others reclined in the visitor's gallery, Sen. Virgil Good (D-Franklin) continued the filibuster by reading a newspaper review of the film "Coal Miner's Daughter."

Then, as suddenly as it began, the filibuster ended after 1 1/2 hours when the Senate leadership promised not to convene the Finance Committee until Saturday morning.

"Both sides know what's at stake (Saturday)," said Senate Majority Leader Hunter B. Andrews as weary senators headed into a night of more closed-door maneuvering.

Earlier in the day, Northern Virginia lawmakers had optimistically pushed the proposed 1 percent sales tax increase that was hammered out by the region's senators in a series of meetings yesterday and this morning. Their chief concern was that the 4 percent gasoline tax they had originally endorsed, combined with the two-cent Dalton tax, would mean at least a seven-cent-a-gallon increase this summer. With an expected rise in gasoline prices, they were afraid a gallon would cost 10 cents more by the end of the year.

"If we vote to put a seven-cent increase on a gallon of gasoline this year, we're going to be lynched," Sen. Adelard L. Brult (D-Fairfax), one of the principal movers behind the new proposal.

With backing from Andrews and powerful Senate Finance Chairman Edward E. Willey (D-Richmond), the bill slipped through the committee this morning in less than 30 minutes by a 14-to-1 vote and glided easily through the full Senate with no debate by midafternoon.

Del. Warren G. Stambaugh (D-Arlington), senior Northern Virginian on the House Finance Committee, believed he had the 11 votes necessary for passage there. But Committee Chairman Archibald A. Campbell (D-Wythe), who had kept the Dalton tax bill bottled up for more than five weeks before it passed over his objections, vowed a fight.

"There's no way I can support it," said Campbell, who argued that approval of the increase for Northern Virginia would amount to "a Balkanization of the sales tax."

"Pass it this year, and next year you'll see Tidewater and Richmond and every place else coming down here," he said. "It will creep all over Virginia."

Even among the Northern Virginians, support for the new scheme was far from unanimous.Some lawmakers were particularly uncomfortable that the increase -- which would have brought the region's sales tax to 5 percent, the same rate in effect in Maryland and the District of Columbia -- would raise the food tax that many of them had worked unsuccessfully to repeal.

"It's amazing," said Del. Robert E. Harris (R-Fairfax0, one of the dissenters. "Here you've got all these legislators who wanted to eliminate the food tax, and now on the last two days of the session they're supporting a bill to raise the food tax 25 percent."

One of the key votes against the bill on the House committee came from conservative Fairfax Republican John S. Buckley, who said he opposed the measure because it failed to include a referendum for Northern Virginia voters.

Dalton's statewide gasoline tax, which passed the House two days ago after intensive lobbying by the Republican governor and legislative leaders, also ran into a parlimentary obstacle on the Senate floor after breezing through the Senate Finance Committee this morning by 13 to 2. Eleven senators balked at approval of a routine procedural move to bring the bill up for a floor vote today.