Tom Rizzo, spokesman for the U.S. Postal Service in northern New England, said it is still too early to know exactly what kind of impact the layoff of 120,000 Postal Service workers nationwide might have in Maine.

Rizzo said he thinks the cuts would likely affect northern New England proportionately to the rest of the country.

National and local unions reacted furiously Friday to a proposal by the Postal Service to lay off the workers by breaking labor contracts and shifting workers out of federal employee health and retirement plans into cheaper alternatives.

John Riley, former president of the American Postal Workers Union in Portland, called the proposal “the fight to end all fights.”

“This is part of a right wing push to manufacture ‘crises’ that are not real to destroy unions and the middle class,” Riley wrote in a mass email he sent Friday to postal employees in Maine. “Unfortunately, it is being enabled by weak Democrats and a President who barely seems to be aware there is a labor movement and working class.”

The Postal Service has lost some $20 billion in the last four years amid a 20 percent drop in mail volume.

Labor experts and other unions also sounded the alarm that any move by Congress to break postal contracts would further wound an already ailing labor movement, much as former President Ronald Reagan’s firing of striking air traffic controllers did in 1981.

Tim Doughty, president of the APWU Portland area Local 458, called the effort to dissolve the latest postal contract signed in May “astonishing” and an action that “reaches well beyond the labor movement.”

“The consideration to renege on an agreement is a troubling concept and it is akin to the latest debate to consider defaulting on our debts,” Doughty wrote in an email expressing his concerns. “Are we a society that is true to our word or are we deteriorating into a society where a man’s word is meaningless and a government commitment isn’t worth the paper it’s written on?”

Rep. Chellie Pingree, a Democrat who represents Maine’s 1st Congressional District, said in a written statement that she is “very disappointed with this proposal to allow the postal service to break its labor contracts.”

“I haven’t been able to review the exact language yet, but I’m almost certain that I would vote against it,” she said. “It would set a terrible precedent and needlessly impact thousands of workers. Employees have held these contracts up in good faith, and the postal service should hold up its end of the bargain.”

Pingree is co-sponsoring legislation that would require the Office of Personnel Management to recalculate payments to Postal Service pension accounts using newer technology.

“I know the postal service is facing difficult times, but there are more responsible ways to approach the problem,” Pingree said. “Going back on agreements with their employees and closing small-town post offices like ones that are essential here in Maine would just make things worse.”

If the Postal Service has overpaid its pension obligations, as some studies have suggested, any overpayments would revert to the Postal Service to relieve its financial crisis.

Doughty said that in addition to overpaying retirement benefits to the tune of $50 to $75 billion, the Postal Service is required by Congress to pay about $5 billion each year to prefund retiree health benefits.

“No other federal agency is required to pay these exorbitant fees and the requirement is simply an extortion ploy by Congress to balance their books on the sweat and labor of the Postal Service employees,” he said.

Republican Sen. Olympia Snowe said in a written statement that while times are tough for families and businesses alike, “the current financial challenges faced by the U.S. Postal Service should not preclude the preservation of universal postal service and convenient community access, which together constitute the bedrock of towns large and small across the nation.”