U.S. banks should be ready to abide by new credit card rules set to take effect over the next two weeks, or they could face punishment from regulators, the Federal Deposit Insurance Corp. told banks last week.

The agency said in a letter that banks should be ready to comply with rules that require them to warn customers 45 days before any interest rate increase and to mail monthly statements at least 21 days in advance.

"The FDIC expects that card issuers it supervises have begun planning for compliance," the agency said in the letter, warning that it is "focused on enforcing compliance."

The changes, set to go into effect Aug. 20, are part of broader credit card legislation enacted by Congress this year.

Banks also will be required, beginning in August 2010, to review any interest rate increases they have put in place since the beginning of this year for a possible reduction.

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