“This extraordinary volume of comments reflects the importance of debit cards as a method for consumers and others to access deposit accounts to make payments for purchase throughout the economy,” Bernanke wrote.

Sen. Jon Tester (D-Mont.) was hoping to capitalize on Bernanke's concerns by offering his legislation to delay implementation by two years as an amendment to a small business bill pending on the Senate floor. At press time, sources estimated that there were between 53 and 55 votes for the amendment, short of the 60 needed to break a filibuster that Senate Majority Whip Richard Durbin (D-Ill.) said he would lead. Durbin sponsored the amendment to last year's financial overhaul bill that ordered the Fed to write a rule regulating interchange fees.

However, two lobbyists pushing for the delay, who requested anonymity, said they sensed the momentum was in their favor and that they were cautiously optimistic that there might be a resolution of the issue within the next few weeks.

Tester's bill would delay implementation by two years and a companion bill in the House, introduced by Rep. Shelley Moore Capito (R-W.Va.), would delay it by one year. Both bills call for a study of the issue by several banking regulators, including the NCUA.

CUNA President/CEO Bill Cheney said in a statement that Bernanke's announcement is “further proof that Congress must take action now to postpone this entire matter. We remain deeply troubled overall by the impact of the statute itself and will continue to urge Congress to adopt legislation to delay the overall implementation date of July 21 and carefully study the impact of the debit interchange provision, particularly on credit unions and their members.”

NAFCU has been working toward the same goal and Brad Thaler, the association's vice president for legislative affairs, expressed concern that if there is no delay, it will cause problems for credit unions.

“Congress should delay the implementation because it is a complex issue and would have far reaching implications,” he said. “If there is no delay it will give credit unions little time to make the adjustments needed to comply with the rule.”

CUNA Deputy General Counsel Mary Mitchell Dunn said the uncertainty means that credit unions probably won't know until the last minute whether the card companies will provide a two-tiered system and what kinds of losses credit unions might face. In addition, she noted that credit unions won't know how long they will have before they will have to be on more than one payment network.

Both trade associations are doing extensive grassroots lobbying and direct contacts with lawmakers, on their own and through the Electronic Payments Coalition.

That group set up a website, www.dontmakeuspay.org, to facilitate e-mail correspondence between executives of financial institutions and their members or customers.

In a letter to lawmakers, NAFCU Executive Vice President Dan Berger wrote that the rule would “devastate our nation's credit unions and the 92 million members they serve.” And he asked, “Isn't it more important that action to significantly alter our nation's electronic payments system, one of the backbones of the 21st century economy, is done right rather than quickly?”

According to the proposed rule, the allowable costs for interchange would be limited to no more than the issuer's allowable costs divided by the number of electronic debit transactions on which the issuer received or charged an interchange transaction fee in the calendar year. Or the issuer could receive interchange capped at 12 cents.

According to the provisions of the financial overhaul bill passed by Congress last year, the final rule was to be approved by April 21 and in effect by July 21.