It's no surprise that banks are pushing rewards cards given their popularity with consumers. The catch is that the cards being offered are now more likely to have annual fees.

In the third quarter, 28 percent of rewards card offers came with annual fees, up from 21 percent in the same period last year, according to market research firm Synovate, which tracks credit card mailings to households.

And just one month into the fourth quarter, 36 percent of rewards card offers had annual fees.

The spike in October is expected to persist, said Anuj Shahani, Synovate's director of competitive tracking services.

In general, rewards cards — typically reserved for those with good to excellent credit — are also accounting for a greater portion of credit card offer mailings. They made up 88 percent of offers in the third quarter, up from 65 percent last year and 58 percent in 2007.

The shift isn't surprising, since banks are focusing on the most creditworthy customers to limit risk in the downturn, Shahani said.

Certain types of rewards cards are more likely to have annual fees, such as those cobranded with an airline or hotel, and exclusive cards that offer richer membership rewards. The American Express Preferred Rewards Gold card, for example, costs $125 a year after the first year.

Another reason banks are pushing rewards cards is that customers tend to use them more frequently in an effort to rack up points. That brings in greater profits from merchants who are charged a fee whenever customers use credit or debit cards, said Ben Woolsey, director of consumer research for CreditCards.com.

Annual fees aren't typical for basic rewards cards. However, analysts have predicted fees could become more common in light of the new federal regulations limiting banks ability to hike interest rates. Citi, for instance, started testing a $30 annual fee on its Diamond Preferred card earlier this year.

The data from Synovate also suggests issuers are rolling out more tiered offerings, meaning richer rewards are coming at a higher price. For example, American Express introduced the Hilton Surpass card in February. For a $75 annual fee, customers get nine points for every dollar spent, compared to six points with the no-fee Hilton card.

Despite the growth in rewards card offerings, overall credit card mailings have been down sharply. There were 272.5 million mailings in the third quarter, down from 939.9 million mailings the same time last year and 1.29 billion in the third quarter of 2007.