Executives of Citigroup Inc., the nation's largest bank, are considering cutting about 15,000 jobs as part of a $1 billion restructuring effort, The Wall Street Journal reported. Citigroup, which announced a cost-cutting review of operations last year, is planning the measures as a result of heavy criticism from investors as its expenses grew faster than its revenues last year and reduced profits. The review is being led by Roger Druskin, the company's chief operating officer, who is set to report his recommendations internally by the end of the week. Citigroup is expected to disclose the cost-cutting plan on or before April 16 when it announces its first-quarter results. Although the plan isn't final, the Journal reported that one possibility Citigroup is considering is a roughly 5 percent reduction in the company's worldwide work force of 327,000. Sources close to the matter say the reduction could be achieved by not replacing some of the 30,000 to 50,000 employees who leave the company each year.