WASHINGTON — The federal agency that insures the private pensions of 44 million workers is having big problems of its own, hitting a deficit of $22.8 billion as big airlines in bankruptcy dump liabilities.

With billions flying out the door of the Pension Benefit Guaranty Corp., concern has been mounting over its financial footing.

The PBGC disclosed in an annual report yesterday that as of Sept. 30, it had about $56.5 billion in assets to cover $79.2 billion in pension liabilities.

Without a legislative overhaul of the private pension system, the PBGC eventually will run out of money to pay the pension claims of the retirees of companies whose plans it has assumed, the head of the agency warned. That would raise the possibility of a taxpayer bailout.

Traditional employer-paid pension plans, giving retirees a fixed monthly amount based on salary and years of employment, are now estimated to be underfunded by some $450 billion. That could jeopardize the retirement security of millions of Americans, lawmakers say.

There has been an explosion in recent years in the number of big, ailing companies — especially in such industries as airlines and steel — shifting their pension liabilities to the PBGC.

"Unfortunately, the financial health of the PBGC is not improving," the agency's executive director, Bradley D. Belt, said in a statement. "The money available to pay benefits is eventually going to run out unless Congress enacts comprehensive pension reform to get plans better funded and provide the insurance program with additional resources."

The PBGC's $22.8 billion deficit for fiscal 2005 takes into account both the pension liabilities the agency has assumed and those it expects to take over in the future.

It is slightly narrowed from the record $23.3 billion shortfall it reported a year ago. If events such as corporate bankruptcies that occurred after the Sept. 30 end of the fiscal year had been counted, the 2005 deficit would have been $25.7 billion, the agency said.

Signaling a deepened future risk, the PBGC said its estimate of "reasonably possible exposure" from companies that could default on their pension payments hit a record $108 billion this year, up from $96 billion in 2004.

For the fiscal year, the PBGC assumed 120 terminated pension plans. It reported $4 billion in losses from pension liabilities while it collected only $1.5 billion in insurance premiums from companies. The agency earned $3.9 billion in investment income.

Treasury Secretary John Snow said the deficit "reminds us that action to reform America's pension system cannot wait any longer."

United Airlines and US Airways used bankruptcy earlier this year, with judges' blessings, to slash costs by dumping their employee pension liabilities — a combined $9.6 billion — onto the PBGC.

Delta Airlines and Northwest Airlines, which both filed for Chapter 11 bankruptcy protection on Sept. 14, may do the same. The pension plans of the nation's No. 3 and No. 4 airlines are underfunded by an estimated $16.3 billion.

And there is speculation that auto parts maker Delphi Corp., which filed for protection from creditors last month, also could end its pension plan and transfer liability to the federal agency.

For months, lawmakers have been grappling with an overhaul of the rules governing company pension plans to tighten controls over employers with underfunded plans and shore up the PBGC's finances.

A key House committee last Wednesday cleared legislation on the matter, advancing what could be the most important retirement issue Congress will address this year as Social Security's overhaul has faded into the background.

The full House could take up the bill as early as this week.