The Arlington County Board proclaimed unanimously yesterday that state and federal authorities should not consider widening Interstate 66, stoking the feud that has erupted between Arlington and its neighbors over how best to cure traffic congestion along the roadway.

Near the beginning of its routine meeting, the five-member County Board passed a resolution insisting that public transportation and other alternatives must at the very least precede road widening. Later board members said that, despite the language, adding one or more lanes to the four-lane highway was completely out of the question and that a lawsuit was under consideration.

"We're prepared to use legal action," said board Chairman Paul F. Ferguson (D), adding that the board is in touch with a prominent transportation lawyer but has not retained him.

"We're not litigious," Ferguson said. "Taking legal action is an absolute last resort."

Rep. Frank R. Wolf (R-Va.), who has led the widening effort, had no comment.

Mark Miner, a spokesman for Gov. James S. Gilmore III (R), who favors widening the highway, called the talk of a lawsuit "unfortunate," particularly when "the governor is trying to put forward a comprehensive, reasonable plan that addresses Northern Virginia's transportation needs."

But Miner also said the governor "realizes the concerns of the people of Arlington" and will listen to them.

The issue arises from a 1977 agreement between then-U.S. Secretary of Transportation William T. Coleman Jr. and the state of Virginia. In the so-called Coleman Decision, Arlington agreed to drop its opposition to the construction of I-66 in exchange for certain promises, including a four-lane limit, sound barriers, and truck and car-pool restrictions.

Since then, some of those limits have been amended, including the addition of a fifth lane along portions of I-66 in Arlington and the allowance of two-person car pools instead of the initial HOV-3 restrictions.

This year, Wolf, who represents part of Fairfax County but not Arlington, led an effort to widen I-66 to at least five lanes through the county. Gilmore joined Wolf in that position, and in October, Congress passed a bill voiding the Coleman Decision.

A spokesman for the Arlington Coalition for Sensible Transportation, a new organization fighting the widening effort, called the proposal to add more lanes as innovative as "disco and bell bottoms."

"We need to look at innovative solutions, not just widening of roads, which has been proven not to work in other places around the country," said Charles Denney, a member of the coalition's steering committee.

Yesterday's resolution proposes a comprehensive study of the corridor, which would consider options such as telecommuting, "live-near-your-work" incentives, bus rapid transit and car-pool restrictions in both directions at rush hour.

"It's not possible to create enough roadways to move everybody in cars," said County Board member Chris Zimmerman (D), who drafted the resolution. "There's no way we'll ever be able to widen the road enough if that's the solution."