Sens. Sherrod Brown (D-Ohio) and David Vitter (R-La.) sent a letter today to regulators arguing for tougher rules on bank capital reserves, the New York Times DealBook blog reported today. "With financial regulators considering a host of new domestic and international capital requirements, we write today to urge your agencies to simplify and enhance the capital rules that will apply to U.S. banks," according to the lawmakers' letter. The two men, who sit on the Senate Banking Committee, addressed the letter to three prominent regulators: Ben S. Bernanke, the Federal Reserve chairman, Martin J. Gruenberg, acting chairman of the Federal Deposit Insurance Corp., and Thomas J. Curry, head of the Office of the Comptroller of the Currency. Brown and Vitter took up the issue in August in a letter to Bernanke, responding to the Fed's decision to support capital rules drafted by an international group of officials known as the Basel Committee on Banking Supervision. Those rules, called Basel III, would require banks to hold the equivalent of at least 7 percent of their assets in so-called Tier 1 common capital. Banks considered "systemically important" - those whose failure could threaten the financial system - would be required to hold capital above that amount.