When Goldman Sachs last summer arranged an $835 million loan to Banco Espírito Santo, it was the result of a concerted, months-long effort by senior Goldman officials to win business with the large Portuguese company, according to people familiar with the matter.

Today, Goldman's embrace of Espirito Santo has come back to haunt the Wall Street giant. Weeks after Goldman arranged the loan, Banco Espírito Santo collapsed amid allegations of fraud. Goldman now is in an unusual public fight with Portugal's central bank, which bailed out Espírito Santo, over whether the loan should be fully repaid. Anticipated losses linked to the loan took a bite out of Goldman's already-weak fourth-quarter results, executives said last week.