San Francisco ? While millions of borrowers are basking in low interest rates, refinancing their mortgages and buying new cars, other consumers are watching their credit card rates climb further into the stratosphere to 30 percent and beyond.

Providian Financial Corp. recently raised the rate on its high-risk accounts from 23.9 percent to 29.9 percent, a move that threatens to drain thousands of dollars from financially strapped households during the next few years.

The strategy is part of the credit card industry’s attempt to boost profits in a sagging economy. Lenders believe they can offset some losses by collecting more from borrowers who have been flagged as the most likely to miss payments.

The new rate at Providian, which is nursing an ailing loan portfolio, affects about $5 billion in outstanding loans nationwide.

The San Francisco-based company said the 29.9 percent rate would apply to 3.3 million of the 18.5 million account holders on its books as of Sept. 30.

Providian’s higher rates have infuriated many customers, but the lender believes the risks posed by the affected customers justifies the move, said Konrad Alt, Providian’s chief public policy officer.

“If people don’t like it, they can try to find a better deal someplace else,” Alt said. “People always have the option of paying off their balance and closing their accounts.”

Providian isn’t the only lender imposing hefty finance charges at a time when many short-term interest rates are falling to their lowest levels in decades.

Atlanta-based CompuCredit Corp. charges 35 percent for an Aspire credit card issued to its high-risk customers. The 35 percent rate applies to about 12 percent of CompuCredit’s loan portfolio, which stood at $1.8 billion as of Sept. 30, said Nancy King, director of investor relations.

Despite such increases, the average credit card interest rate nationwide stood at 14.41 percent in November, down from 16.57 percent at the start of 2001, according to CardWeb.

That drop reflects the overall decline in interest rates, and credit card companies’ efforts to increase business from their best customers by offering rates in the very low single digits.