NEW YORK (TheStreet) -- A debate is heating up in Washington over whether the 40-year ban on U.S. crude oil exports should be lifted. Sen. Lisa Murkowski (R-Alaska) is sponsoring the Energy Supply and Distribution Act of 2015, which would allow U.S. companies to export oil again.

"This is an opportunity for us to become an energy superpower," she told her fellow lawmakers in a Senate hearing on Tuesday. She also said lifting the ban would enable the U.S. to use its energy resources as a "diplomatic tool."

Murkowski and co-sponsor Sen. John Hoven (R-N.D.) said lifting the ban could be good for consumers at the pump. "More supply puts downward pressure on prices," Hoven said.

But some argue the bill could raise costs for U.S. refineries, which turn crude oil into gasoline. The nation's refineries have access to U.S. oil, known as West Texas Intermediate, which is generally cheaper than oil pumped overseas at Brent crude prices. That gives them a cost advantage over their international competitors.

West Texas Intermediate was trading in the neighborhood of $48 a barrel Tuesday afternoon, lower than Brent's price of around $53.50.

The additional cost to U.S. consumers if the export ban was lifted would add up to $25 billion a year, or $125 per driver and $257 per family, Leo Gerard, international president of the United Steelworkers, a union with 30,000 members working in the oil and refining industry, told lawmakers. "In extreme cases it could cause U.S. refineries to close, which could endanger supplies of other refined products such as home heating oil in the Northeast."

Shares of refinery operators Marathon Petroleum (MPC - Get Report) and Valero Energy (VLO - Get Report) posted modest gains on Tuesday, while Phillips 66 (PSX - Get Report) rose 2.9%.