Overseas Shipholding Group Inc., the largest U.S. tanker operator, won approval to borrow $25 million to maintain ships and to make payments to two lenders that funded construction of its vessels, Bloomberg News reported yesterday. Bankruptcy Judge Peter Walsh said yesterday that he would approve the loans after a group of Overseas's lenders dropped their opposition to the financing. The New York-based company filed for bankruptcy last year after global shipping rates fell and the company gave up trying to win a federal loan guarantee. Overseas listed assets of $4.15 billion and debt of $2.67 billion in its chapter 11 filing.