A Federal Reserve rule capping debit-card "swipe" fees set by Visa Inc. and MasterCard Inc. would be delayed at least six months under a plan introduced in the U.S. Senate.

Senators began considering language today from Senators Jon Tester, a Montana Democrat, and Bob Corker, a Tennessee Republican, that would let federal regulators study the issue before determining whether to write new rules. The caps, mandated by the Dodd-Frank Act, are set to take effect July 21.

The Fed would get an additional six months if the study shows the current proposal would hurt consumers or fail to protect banks and credit unions with less than $10 billion in assets. In December, the central bank proposed capping the swipe fees, or interchange, at 12 cents a transaction, replacing a formula that averages 1.14 percent of the purchase price.