Virginia Gov. John N. Dalton, who as steadfastly rejected any suggestion of a tax increase, said yesterday he may support a proposed higher gasoline tax to salvage the state's faltering highway construction program.

"I'm very concerned whether we'll have any money at all for highway construction," Dalton told a press conference at the State Capitol in Richmond.

With inflation driving construction costs up sharply and increasingly fuel-efficient cars cutting into gasoline tax revenues, the state highway department said yesterday it has had to slash in half monthly spending for construction projects.

Dalton said he will not make any tax recommendation until he gets revenue projections from the highway department and estimates on how much it will need to maintain an adequate repair program.

If Dalton proposes a gasoline tax increase in Janurary when the legislature convenes, he may not be alone. Maryland is also facing a highway revenue gap, and House Speaker Benjamin Cardin (D-Baltimore) said yesterday the legislature will take up the question of imposing a percentage tax that would increase receipts as inflation grows. "It will be a major issue when the legislature convenes in January," Cardin said.

The department has warned that, if Virginians continue to cut back on driving, revenues from the current 9-cent-gallon gasoline tax could fall short by $60 million or more. Because road maintenance gets top proprity, any shortfall would have to be absorbed entirely by the state's construction program.

According to Virginia officials it would take a two-cents-a-gallon increase of make up for that shortfall. Each penny increase in the Virginia tax yields about $30 million annually, officials said. A penny increase would cost the average driver about $10 a year, the officials estimate.

"I don't expect the downward trend to continue," said Deputy Highway Commissioner Leo E. Busser iii yesterday. "But you don't know, what with they're blowng up oil wells in Iran."

The Virginia construction program will lose an estimated $175 million over the next two years because of higher costs and inflation, he said.

Just how far behind the department has fallen can be gauged by comparing local construction requests -- $3 billion this year -- with the available funds -- $463 million. Though the local requests are supposed to include only projects deemed necessary, their dollar total was almost seven times what the department has to spend.

Though the price of gasoline has been skyrocketing, the state gasoline tax has stayed the same since 1972, when it was increased from 7 to 9 cents. There have been suggestions in recent years that it should be increased, but the state's conservative legislature has been wary of increasing any taxes.

During that period, thousands of cars have been added to Virginia roads, but increased consumption has been offset by new, more fuel-efficient automobiles.

"The big problem . . . in the years to come is that we're going to be having automobiles that will get 26 to 27 miles to the gallon . . ." Dalton said.

Some Northern Virginia legislators have been eyeing the shortfall in highway trust monies for several months. They are privately hopeful that they can trade support of any proposed increase in the gasoline tax for increased taxing powers needed to fund the Metro transit system's Virginia operations. Dalton has refused to endorse a proposal for a regional tax devoted to the transit system, but some legislators are saying that he may have to change his position to get support for a higher gasoline tax.

The Carter administration has told Virginia that it will fund much of the subway's construction costs, but has insisted that the state pledge a "stable and reliable" source of funds to meet the system's operating costs.

But with an election only a little more than two weeks away. Virginia legislators have not been eager to announce they will be fighting for imposition of a higher tax or even one aimed at helping the now highly popular subway.

There are some Northern Virginia officials who think that the highway department also needs a more stable and reliable source of revenue. Fairfax County lawyer, MARC E. Bettius, who won the recent court decision that frees developers from paying for improvements to public roads adjacent to their projects, said he is organizing a group of zoning attorneys "to present a positive case."

Bettius said he wants the group to explore a variety of ways that the highway department can get enough funds to both maintain roads and carry on needed expansion. But he said the state should take a bolder lead in encouraging developers and localities to institute traffic controls that would put a brake on the need for highway funds.