NEW YORK - Roger Wald recently discovered he would save $25,000 a year if he refinanced his five-year mortgage at 4.75 percent. Wald, an auto body repairman in Sarasota, Fla., could have gotten that rate last month.

But like many homeowners, he waited for rates to fall further. Now, he's worried he missed his chance.

Mortgage rates at some lenders spiked by as much as 1 percent on Wednesday and saw little relief on Thursday, according to mortgage brokers.

"The 4.75 percent my broker quoted two weeks ago? There's no way I'm going to get that now," said Wald, 49.

The fear dogging homeowners and investors alike is that April's record lows in mortgage rates may have come and gone.

The stock market has rallied since early March on the assumption the economy will rebound later this year. Federal Reserve Chairman Ben Bernanke has been calling early signs of economic stabilization "green shoots" - and one of those shoots was a pickup in refinancing activity caused by tumbling mortgage rates.

But mortgage rates have rebounded sharply over the past few days as the nation's growing debt raises concerns that government-backed assets could lose some of their value. It's a trend that could slow both refinancing and home buying if it continues. Higher mortgage rates won't necessarily derail the economy's recovery, analysts say, but it certainly won't help.

"If the Fed does not step in, you are going to see the 'green shoots' get frost bite," said T.J. Marta, founder of financial research firm Marta on the Markets.

The average rate for a 30-year fixed mortgage was back at 4.91 percent last week, Freddie Mac said Thursday.

The 30-year fixed mortgage rate hit a record low of 4.78 percent in April thanks in large part to the Fed's decision this year to buy as much as $1.25 trillion in mortgage securities and $300 billion in Treasury notes. So far, the Fed has bought $130.5 billion in government debt and more than $431 billion in mortgage securities.

Lower rates led to a surge in mortgage applications. Applications rose for five straight weeks between early March and early April, according to the Mortgage Bankers Association.