ATLANTA - More pain at the pump is on the way for Georgia motorists, as the state's gas tax is set to rise by about 3 cents a gallon on Sunday as a result of a formula tied to fuel prices.

The increase - which also will add an additional two cents a gallon in many counties - takes effect as part of a tax rate change that usually takes place twice a year. Part of the state gas tax is pegged to the average price of gas, and when that price rises, the tax jumps as well.

Gov. Nathan Deal, a Republican who could issue an executive order to freeze the rate, said it was unlikely he would do so.

"I think it's real unlikely that we would put a freeze on it," Deal told reporters Tuesday at a press conference. "I think for a change to be made it's something the General Assembly should take up rather than the governor just ad hoc on his own taking action on it."

Deal's predecessor, Gov. Sonny Perdue, halted what would have been a 2.9-cent-per-gallon jump in June 2008, saying the state should not reap a $70 million to $80 million tax windfall because of spiking pump prices. He also suspended the state sales tax on gasoline for a month in 2005 as prices soared in the wake of Hurricane Katrina.

The gas tax issue has long frustrated Georgia motorists, and lawmakers this year considered making changes to the gas tax rules but adjourned without taking action.

Georgia's gas taxes are made up of several moving parts. The first is a charge of 7.5 cents per gallon that doesn't change. The second, though, is a more volatile per-gallon charge that can go up or down as the gas price fluctuates. Many Georgia counties impose a third additional fee that's also pegged to gas prices.

Prices at Georgia's pumps have soared this year partly because of disruptions in oil production due to the conflict in Libya. President Barack Obama has urged major oil producers such as Saudi Arabia to increase their supply as oil prices soared well beyond $100 a barrel.

Gas in Georgia is now averaging $3.76 a gallon, according to the AAA Daily Fuel Gauge Report. That's slightly below the national average of $3.88 per gallon, but a far cry from the $2.77 per gallon price average in Georgia from a year ago.

Deal spokesman Brian Robinson explained why the governor decided against issuing a freeze.

"We are not in a state of emergency. There are not supply line disruptions," he said. "These are prices that are affecting everyone globally. And outside a state emergency, the governor doesn't believe he should be suspending state law. If the General Assembly wants to tackle this, they can."

Some Georgia motorists are frustrated that gas prices continue to rise just as the nation's economy appears to be starting to rebound. Robin Sheppard, an insurance underwriter, urged Deal to step in.

"I'm absolutely upset," said Sheppard, who said she spends about $100 a week to fill up her Chevy Tahoe driving from Braselton to her office in Duluth. "It's basically a small mortgage payment