The four largest U.S. banks face potential losses of $26 billion over the next several years from their exposure to private-label mortgages and potential losses from delinquency, analysts at Goldman Sachs said. Private-label mortgages are those offered by private institutions, as against those by government-backed agencies. The brokerage said $28 billion of market cap was lost between — Bank of America Corp, JPMorgan Chase & Co, Citigroup and Wells Fargo & Co — as the market attempted to price in the potential impact of losses on private label securities.