WASHINGTON – Homeland security officials on Friday hinted at a possible face-saving deal to end their standoff with a handful of states, including Maine, over new driver’s license rules – a dispute that, left unresolved, could cause big air travel headaches.

For weeks, the Homeland Security Department has been headed toward a showdown with some states over a law called Real ID, which would require new security measures for state-issued driver’s licenses. Yet a letter late Friday from a top DHS official suggested Washington may be backing away from a messy fight.

South Carolina, Maine and Montana are the only states that have not sought extensions to comply or have not already started toward compliance with Real ID, which was passed after the 2001 terror attacks on New York and Washington.

On Friday, the federal agency granted Montana an extension, even though state officials didn’t ask for one and insist they will not adhere to the Real ID law.

Montana Gov. Brian Schweitzer told The Associated Press that DHS “painted themselves in a corner.”

A fourth state, New Hampshire, has asked to be exempted, but Homeland Security officials have not found that letter legally acceptable, so the Granite State has not received an extension.

Homeland Security Secretary Michael Chertoff had warned that if holdout states do not send a letter by the end of March seeking an extension, come May residents of such states will no longer be able to use their driver’s licenses as valid ID to board airplanes or enter federal buildings.

Such travelers would instead have to present a passport or be subjected to secondary screening.

Maine Gov. John Baldacci plans to respond by the March 31 deadline. The governor’s staff on Thursday was continuing to review the waiver language to see what is the best way to respond to Homeland Security, but his press office said that doesn’t mean the state will seek an extension. Baldacci has said he does not want Mainers inconvenienced because they lack sufficient credentials.

Five senators – Susan Collins and Olympia Snowe of Maine, Jon Tester and Max Baucus of Montana, and John Sununu of New Hampshire – appealed to Chertoff last week to exempt all 50 states from the looming deadline.

Chertoff responded that it was not he but Congress that picked the date when the law went into effect in 2005.

“You may disagree with the foregoing law, but I cannot ignore it,” Chertoff said in the letter.

The law is necessary for national security, according to recommendations from the commission that studied the Sept. 11, 2001, attacks, he said.

Collins expressed disappointment Friday with Chertoff’s decision not to provide a blanket exemption for all 50 states, and she urged that Maine formally request an extension.

“With a single, one-sentence letter, the state of Maine can request an extension, thus ensuring that Mainers will still be able to use their drivers’ licenses to board planes and access federal buildings when the regulations go into effect on May 11, 2008,” Collins said in a statement. “While I remain concerned about the cost and privacy issues associated with Real ID, I continue to urge the state to request this extension, which in no way commits it to future compliance with Real ID but rather would avoid tremendous inconvenience for Maine citizens.”

Snowe criticized the Department of Homeland Security’s failure to grant Maine an implementation waiver.

“At a time when the state of Maine is addressing a significant budget shortfall, this is the wrong time to impose a federal mandate that will adversely impact Maine’s ability to achieve financial solvency,” Snowe said in a statement.

Hours after Chertoff sent his letters Friday, DHS Assistant Secretary Stewart Baker wrote to the attorney general of Montana, saying that even though the state was explicitly not seeking an extension, it would be granted one anyway. Baker reasoned the state’s new license security measures already met many of the Real ID requirements anyway.

“I can only provide the relief you are seeking by treating your letter as a request for an extension,” Baker wrote.

Schweitzer, Montana’s Democratic governor, said his state had not backed down.

“We sent them a horse. If they choose to call it a zebra, that is their business,” said Schweitzer.

The agency’s approach to Montana could provide an easy way out for the remaining states resistant to Real ID and suggests the federal government doesn’t want to go ahead with its plan to conduct extra screening on residents of certain states.

If the two sides can’t cut a face-saving deal, Chertoff has offered a blunt warning to those critics who claim the government is bluffing. “Showing up at the airport with only a driver’s license from such a state will be no better than showing up without identification,” he wrote to the senators. “No doubt this will impel many to choose the inconvenience of traveling with a passport.”

The end of the standoff with Montana does not necessarily mean the entire fight is over.

South Carolina Gov. Mark Sanford was considering legal action, and the state’s attorney general was preparing an opinion on whether the governor would have a case if he decided to sue the federal government. A spokesman for Attorney General Henry McMaster said the opinion will be released Monday.

Chertoff has offered a plan to gradually implement Real ID requirements over a period of 10 years, so that eventually all driver’s licenses would have several layers of security features to prevent forgery. They would also be issued only after a number of identity checks, including immigration status and verification of birth certificates.

Critics of the plan say it is too expensive, an invasion of privacy, and won’t actually make the country safer.