Nokia Oyj workers are bracing for what may be the steepest job cuts in almost two decades as the world's largest maker of mobile phones prepares to start a partnership with Microsoft Corp.

A reduction in research and development activities is set to be announced by the end of the month, with as many as 6,000 jobs under threat, said Antti Rinne of Pro, Finland's biggest private-sector office-worker union. That would be equivalent to 38 percent of the Finnish company's global devices R&D workforce. Nokia declined to comment on the numbers.