NEW YORK (Reuters) - An estimated 1.3 million car workers and retirees could see their pensions cut if one or more of the U.S. automakers collapse, the head of the government agency that protects Americans’ pensions warned on Friday.

Charles Millard, Director of the U.S. Pension Benefit Guaranty Corp (PBGC) raised his concerns in an interview with the Wall Street Journal.

He acknowledged that General Motors Corp GM.N, Ford Motor Co F.N and Chrysler LLC have well-funded pensions according to the standard accounting rules applied by the Securities and Exchange Commission.

But by the PBGC’s measures, the pension funds of Detroit’s Big Three would be underfunded by as much as $41 billion if one or more of the automakers went under and killed their pension plans, the Journal report said.

“An awful lot of people seem to think these plans are well funded or overfunded,” Millard said in the interview appearing on the Journal’s web site.

“Each of these plans is significantly underfunded (and) in three years I don’t want people coming back and saying, ‘How come the PBGC never told us that?’” he was quoted as saying.

Millard estimates the three carmakers only have enough money in their pension funds to cover 76 percent of obligations they have made, if they terminate the pension plans.

GM’s plan is estimated to be $20 billion, or about 20 percent underfunded, while Chrysler’s plan is 34 percent underfunded, leading to a $9 billion-plus shortfall, the agency said. Ford’s funded ratio is not publicly available, but the company’s pension plans are likely running at a $12 billion deficit, it said.

GM spokeswoman Julie Gibson told the Journal the company is in compliance with pension accounting, its pensions are adequately funded and it doesn’t have any near-term funding obligations.

Ford spokesman Bill Collins said the automaker’s most-recent numbers suggest its U.S. plan is 103 percent funded, or carrying a $1.3 billion surplus with $45.8 billion in plan.

There was no immediate comment from Chrysler.