The biggest U.S. bank holding companies will need to round up as much as $68 billion more in loss-absorbing capital under supplemental leverage ratio rules adopted by regulators yesterday, Bloomberg News reported. Eight lenders, including JPMorgan Chase & Co. and Bank of America Corp., face greater restrictions on borrowing power than their overseas competitors as they meet a demand to hold capital equal to at least 5 percent of total assets. The rules designed to curtail financial-system risk surpass the 3 percent minimum set in a global agreement by the Basel Committee on Banking Supervision. The leverage rule, which also affects Citigroup Inc., Wells Fargo & Co., Goldman Sachs Group Inc., Morgan Stanley, Bank of New York Mellon Corp. and State Street Corp., is meant to work alongside risk-based capital standards approved by U.S. regulators last year and a pending rule that would require banks to keep a high level of ready-to-sell assets to weather a crisis. The rule was approved by the Federal Reserve, Federal Deposit Insurance Corp. and Office of the Comptroller of the Currency.