The Federal Reserve is expected to unveil a proposed rule next week that would limit the transaction fees that banks can charge retailers when a customer uses a debit card, according to two industry sources familiar with the matter.

The rule, mandated by the financial reform law enacted in July, is expected be on the agenda for a December 16 board meeting, according to the sources. Federal Reserve officials have only said publicly that a rule is expected soon.

(Reporting by Dave Clarke)