July 17 (Bloomberg) — Microsoft Corp. said it will eliminate as many as 18,000 jobs, the largest round of cuts in its history, as Chief Executive Officer Satya Nadella integrates Nokia Oyj's handset unit and slims down the software maker.

The restructuring, amounting to about 14 percent of its workforce, includes 12,500 Nokia factory and professional positions — half the number of employees added in the acquisition. At Microsoft, cuts will be in sales, marketing and engineering. The reductions are expected to be completed by June 30, 2015, and will result in a pretax charge of $1.1 billion to $1.6 billion, Microsoft said in a statement today.

Nadella, who took over from Steve Ballmer in February, is retooling the company's structure as it seeks to compete with nimbler rivals offering mobile and Internet-based software and services. He's also working to wring a promised $600 million in annual savings from Microsoft's Nokia deal, which added 25,000 workers in April, bringing the total to about 127,100.