As they work to complete the first phase of a major efficiency program, Bank of America Corp. executives are discussing plans that could slash the companywide workforce by as many as 25,000 to 30,000 jobs, sources familiar with the matter said. The job losses could come over several years, the sources said. The Charlotte-based bank hasn’t said how many jobs will be eliminated in the efficiency campaign, although some reports had previously said the number could reach 10,000. Executives are still working on final plans. Broader cuts would be similar to London-based HSBC’s plan to eliminate 30,000 jobs, or about 10 percent of its workforce. At the end of June, Bank of America employed about 288,000 workers, with about 15,000 in its headquarters city. A 30,000 reduction would equate to just over 10 percent of the employee base.