Gov. Timothy M. Kaine said yesterday that Northern Virginia governments probably will have to assume some responsibility for new local roads -- now planned and paid for by the state -- if they want to reap the benefits of the $1.5 billion-a-year transportation package passed by the General Assembly last week.

Kaine's comments came as Virginia Republicans launched an advertising campaign to try to pressure the Democratic governor to support the GOP-backed transportation plan. As early as today, the state Republican Party plans to air a 30-second television commercial that credits the GOP-controlled General Assembly with approving the plan to reduce traffic.

"Call Governor Kaine. Tell him: 'Start solving problems. Stop playing politics,' " concludes the ad, which will air on network and cable stations in Northern Virginia and Hampton Roads.

Kaine has promised to make significant changes to the transportation bill. He says the plan as drafted would erode critical services by draining money from the state's general fund and shortchange rural communities on road projects. If the General Assembly rejects the amendments, Kaine said, he may veto it.

"If there aren't amendments, there is certainly a possibility of a veto," he said on a radio talk show in Washington.

Fairfax, Loudoun and Prince William county officials have also protested the Republican-backed measure, which would allow them to raise $400 million a year in local taxes and fees for road and transit improvements. As a condition of the new taxing power, however, the counties must agree to take on responsibility for planning and construction of new secondary roads -- a potentially costly proposition. The Fairfax Board of Supervisors approved a resolution Monday calling on Kaine to veto the bill if the provision remained.

On WTOP radio, Kaine said he was eager to sit down with county officials and hear their objections. But he also acknowledged that any legislative compromise is likely to involve increased local responsibility for secondary roads.

"I suspect so," he said after the program. "But we want to make sure that it's fair."

During the program, Kaine expressed optimism about avoiding a veto but said any transportation bill would be meaningless if Northern Virginia doesn't buy in.

"If Fairfax, Prince William and Loudoun pull the plug, then the transportation bill is just a 105-page pile of paper," he said.

Fairfax Board of Supervisors Chairman Gerald E. Connolly (D) said he would not support any bill in which responsibility for new secondary roads was transferred to localities.

"We don't agree with that," he said. "Our board's already spoken on the matter, and Prince William and Loudoun feel the same way. It's going to cost our constituents a lot of money."

Right now, the Virginia Department of Transportation is responsible for planning, design, construction and maintenance of most secondary roads. Under the bill, the state would continue to pay for new secondary roads, but counties would take over planning and construction. For the fiscal year beginning July 1, about $18 million in state money is available for new roads in Fairfax.

But county officials are concerned about a projected decline in available state money, driven by a drop in gasoline tax revenue and the increasing use of construction funds for maintenance of existing roads. In 2004, the county received $29 million in state road funds. By 2012, the projected state contribution will be $9.5 million. Officials say the bill as written could leave the county with increased responsibilities and a dwindling state contribution.

Exactly how much the bill's mandates would cost is still being calculated by county officials. Connolly said it could cost more than the actual value of the transportation package.

While the county is almost fully developed, the costs of redevelopment and revitalization will also be considerable. But Del. David B. Albo (R-Fairfax) said local governments have long requested more control over their local roads. "I think they don't understand the issue yet," he said.

Connolly said the bill was the beginning of a larger strategy of "devolution" pursued by Republican lawmakers interested in ending state responsibility for secondary roads entirely.

Republicans are hitting back. The GOP television ad accuses Kaine of breaking a campaign promise not to seek higher taxes to pay for transportation.

"Another day, another traffic jam!" the ad begins, with a man speaking.

"When will someone do something about Virginia's outdated, overcrowded roads?" a woman replies.

"Someone has," says the man. "The General Assembly plan? Bond money for new roads. Penalties on abusive drivers. Regional solutions. Dedicating our multimillion-dollar surplus to transportation. All without a statewide tax increase. But Tim Kaine is criticizing it, even though he promised not to raise taxes. Call Governor Kaine. Tell him: 'Start solving problems. Stop playing politics.' "

State GOP Chairman Ed Gillespie said: "Through no effort of his own, Governor Kaine now has the transportation plan he promised in 2005. Now isn't the time for listening tours, obstruction or sharp partisanship from the governor. Kaine owes it to Virginians to sign this bill."

C. Richard Cranwell, chairman of the state Democrats, responded: "This is the same Ed Gillespie that used to be in Washington [as national GOP chairman]. The problem is, he can't forget the tricks he learned in Washington and wants to bring them to Virginia. Attacking the governor with a television ad -- it almost borders on being juvenile."

To make his case, Kaine is vowing to have "a very public discussion" with state residents about how they prefer to pay to build more roads and mass transit.

Yesterday he began a five-day series of events designed to highlight his budget priorities, such as boosting funding for health care and enrolling more 4-year-olds in pre-kindergarten programs.

Republicans will counter, Gillespie said, by sending party activists to hold simultaneous events in the towns that Kaine visits. House Speaker William J. Howell (R-Stafford) has scheduled a news conference tomorrow in Richmond to rebut the governor's arguments. Later in the day, he will make his pitch to the Hampton Roads Chamber of Commerce.