Mortgage refinancing? Not for these 2.3 million homeowners.

About 2.3 million homeowners could have refinanced their mortgages last year if they didn't owe more than their homes were worth or if lending standards weren't so strict, according to a Federal Reserve study released Thursday.

Long-term mortgage rates are near record lows and have been below 5 percent for all but two weeks this year. The average rate on a 30-year fixed loan is now 4.09 percent.

But lenders typically require homeowners to have equity in their homes to refinance. And many lenders are approving only borrowers with high credit scores.

Roughly 22.5 percent of homeowners, or about 11 million, are "underwater" — they owe more than their homes are worth — according to CoreLogic, a real estate data research firm.

The figures don't show how many of the homeowners obtained loans during the housing boom, when lending standards were often lax. Many lenders offered loans to people with poor credit, no employment checks and little or no money down.

The Fed said about 4.5 million refinancing applications were approved last year. In a healthy housing market, that figure would be nearly 34 percent higher, it said.

The Federal Housing Finance Agency has said it's reviewing a program it launched two years ago to see if it might be expanded to let more homeowners qualify. The program, called Home Affordable Refinance Program, or HARP, lets people whose homes are underwater by up to 20 percent refinance at lower rates.

But to be approved for the program, homeowners must be current on their mortgages, which must date from 2009 or later.

As of July, about 838,000 homeowners had refinanced through the program. Officials had hoped at least 4 million Americans would take advantage.

The Fed's study reviewed information from more than 7,900 lenders. The number of approved mortgages fell from nearly 9 million in 2009 to fewer than 8 million in 2010. The peak was 15.6 million in 2005.