WASHINGTON (CNN) - The Senate is due to vote at "high noon" Wednesday on a controversial proposal to allow people to carry concealed weapons from state to state.
The measure, which has split Democrats, would require each of the 48 states that currently allow concealed firearms to honor permits issued in other states.
Supporters of the measure argue it would help deter criminals; opponents claim it would endanger innocent people by effectively forcing most of the country to conform to regulations in states with the loosest gun ownership standards.
Sen. John Barrasso, a Wyoming Republican who is a co-sponsor of the amendment, argued Wednesday that gun licenses should apply across state lines, like driver's licenses.
"People travel," he said on CNN's "American Morning."
"We have truck drivers on our roads, people traveling for vacation in their vehicles, and if you have a license... you should be able to use that license in other states. It should apply like a driver's license," he said.
He argued that concealed weapons deter crime.
"Carrying a concealed weapon is a sign of self-defense, self-protection, and I think it lowers crime," he said.
And he said people carrying guns would still have to obey laws where they are.
"The law of the state where that person happens to be at the time are the laws that apply if terms of if you're allowed to carry a gun into a bar or restaurant... State rights continue to apply there."
But Michael Bloomberg, the mayor of New York City and an opponent of the law, said the proposed amendment tramples on states' rights.
"Wyoming shouldn't be subject to New York state laws, and we're going in that direction," he said. "What's right for the people of Wyoming isn't necessarily right for the people of New York and vice versa."
Bloomberg insisted that guns do not make people safer.
"There's no evidence that if you have a gun, you're safer. Quite the contrary. If you have a gun at home, (you are) something like 20 times more likely to have somebody in your house killed," he said on "American Morning."
"We have to protect our policemen, protect our citizens. We can't have all these guns, and it's reasonable to have each state make their own laws," he said.
The issue has blurred Capitol Hill's usual partisan lines. Senate Majority Leader Harry Reid, a Nevada Democrat, is one of several Southern and Western Democrats supporting the measure. Others Democrats oppose it.
The full Senate vote, which Barrasso pointed out was at "high noon" on Wednesday, comes in the form of an amendment to a larger defense appropriations bill.
For gun control advocates, the fight over the proposal is the latest in a series of unexpected setbacks since the start of the Obama administration.
In May, President Barack Obama signed a credit card bill that included a provision allowing people to carry guns in national parks. Another bill that would have given the District of Columbia's representative in Congress full voting rights stalled earlier in the year after Senate Republicans attached a provision that would have eased tight gun controls in the district.
–CNN's Greg Clary and Brianna Keilar contributed to this report