Facing billions of dollars in losses from the subprime mortgage crisis, Merrill Lynch chairman and chief executive, Stanley O’Neal, floated the idea of a merger with a large bank, a foray that angered Merrill’s board and could cost him his job, according to people close to the beleaguered Wall Street firm.

Mr O’Neal broached the possibility of a merger with Wachovia, the bank based in Charlotte, N.C., without first getting the approval of Merrill’s board, a major breach of corporate protocol at a time when directors were already concerned about the company’s performance, these people said.