AUGUSTA -- A plan to make Maine driver's licenses and identification cards more secure is proving to be so controversial in the Legislature that the bill's fate is impossible to predict as lawmakers prepare to take it up this week.

The measure, which closely resembles a bill filed by Gov. John Baldacci, has split the Legislature's Transportation Committee, which voted 8-5 in favor of the legislation. But while most of committee members back the bill, the Democratic co-chairmen of the committee are on opposite sides of the issue.

Also at odds are Baldacci, who supports the bill, and Secretary of State Matthew Dunlap, who opposes it. Dunlap, who oversees the Bureau of Motor Vehicles, says making federally mandated changes now will set Maine on a path toward increasingly onerous and expensive licensing changes in future years.

The stakes for the bill are high. The legislation averts a showdown between the state and the U.S. Department of Homeland Security, which says it would stop accepting Maine driver's licenses as identification for commercial flights and entry into federal buildings unless Maine tightens up its licensing procedures.

When Baldacci agreed earlier this month to propose just such a crackdown, Homeland Security lifted its threat and gave the state an extension to comply with the Real ID Act. That federal law is designed to make state driver's licenses across the country more uniform and secure to fight fraud.

The state legislation supported by a majority of the Transportation Committee would require that immigrants prove they are in this country legally to qualify for a Maine license or identification card. Maine is one of six states that have no such "legal presence" requirement.

The bill also would require that licenses awarded to non-citizens expire when the license holder's legal status here runs out.

Other provisions would force the state to do three things: Verify the documents offered by immigrants seeking licenses, photograph all license applicants at the start of the process and ensure that the state is not issuing multiple licenses to the same people.

The governor's version of the bill would have paid for those changes with a small increase in the cost of non-commercial licenses and by hiring more state tax agents to raise money by ferreting out unpaid business taxes.

But the Transportation Committee balked at the tax-collection crackdown, opting instead for a bigger increase in licensing fees to foot the tab.

Under the bill that is now headed to the full Legislature, the cost of a six-year non-commercial license would jump from $30 to $45.

"At the end of the day, we think it's the right thing to do and we're pushing for its enactment," said David Farmer, Baldacci's spokesman. But Farmer acknowledged that the bill has generated "a lot of opposition."

On one side of the debate are supporters of anti-fraud measures and simplified security checks for Maine travelers. On the other are those who fear this round of reforms will pave the way for complying with the Real ID Act, which they view as a dangerous attempt to effectively create a national ID card that could undermine privacy and encourage identity theft.

Many lawmakers remain undecided on the merits of the bill, according to Dunlap. He said the upcoming floor debates in the House of Representatives and the Senate may be unusually important, as fence-sitting lawmakers look to their colleagues for guidance.

Generally, floor debates on major issues do not affect the outcome very much because legislators usually know where they stand before the debate begins. In this case, Dunlap said, the floor debates may be especially persuasive.

Supporters of the bill say it makes sense for immigrants to prove they are here legally to qualify for a state driver's license, a requirement already in effect in 44 states.

They also say the state has no practical choice but to go along with federal demands because state lawmakers cannot risk inconveniencing Mainers at airports and federal buildings by forcing them to undergo additional screening if they lack passports as an alternative form of ID.

"The fact that their constituents may be stuck in an airport" if the state rejects the reforms will outweigh other considerations, said Rep. Richard Cebra, R-Naples, a member of the Transportation Committee who supports the bill.

"There's very little option for people at this point," he said.

Opponents argue that the federal government is trying to coerce Maine into backing an unfunded mandate that would do little or nothing to promote security.

They also say the election of a new president may trigger the repeal or revision of the Real ID Act, so Maine should wait to see what happens.

"I feel we've been singled out and I'm wondering why and I can't seem to get a true answer," said Rep. Charles Theriault, D-Madawaska, a Transportation Committee member who opposes the bill.

Theriault said some states received quick federal extensions on complying with the Real ID Act without having to promise the kinds of immediate licensing changes that the federal government required from Baldacci.

Maine has until Dec. 15 to make the reforms, so the governor and the Legislature will have time to regroup if the Legislature kills the pending bill this week.

If the state acts by Dec. 15, the conditional extension that the federal government awarded this month will remain in effect until Dec. 31, 2009. The state would then be expected to meet additional requirements spelled out in the Real ID Act.

A separate bill already working its way through the Legislature would restrict driver's licenses to Maine residents, without also tackling the legal status of applicants.

That bill received preliminary approval in the House last week and in the Senate on Monday.