(CNN) -- Two-thirds of Americans would oppose a law in their state that would increase the gas tax to help pay for road and bridge repairs, according to a new national poll.

A Gallup survey released Monday indicates that 66 percent of the public would vote against a state law that would increase the gas tax by up to 20 cents per gallon, with the revenue going towards improving roads, bridges, and building more mass transit. Just under one in three said they would vote for such a measure.

According to the poll, Democrats and westerners are slightly more willing to vote to increase the gas tax, with four in ten Democrats, three in ten independents but just 15 percent of Republicans supportive. Thirty-seven percent of people living the western U.S. would support the move. That drops to 32 percent for easterners and to one in four for those in the Midwest and South.

"It is not clear whether Americans' lack of support for this proposal stems from the type, amount, or purpose of the tax," says a release by Gallup. "Americans may be opposed to increasing the price of gas - a necessary commodity for many individuals - during a fragile economy, regardless of how the resulting funds are used."

Last month Maryland lawmakers passed their first gas tax increase in two decades, with the revenue expected to go towards transportation infrastructure and mass-transit projects. Nearly 20 other states have recently approved or are considering such a tax increase or fee changes to help pay for maintaining roads, tunnels, bridges and mass transit.

The Gallup poll was conducted April 9-10, with 1,018 adults nationwide questioned by telephone. The survey's overall sampling error is plus or minus four percentage points.

CNN Political Editor Paul Steinhauser contributed to this story.

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