Global asset manager BlackRock Inc. (BLK.N) is planning to cut about 400 jobs, or 3 percent of its workforce, as the world's largest money manager tries to streamline parts of its business and bolster areas it believes are poised for growth, a person familiar with the matter said on Wednesday.

In a memo to employees, BlackRock said the job cuts have not yet been finalized and that those affected by the changes will be treated fairly and with respect. The company plans to implement the cuts in the coming weeks, with headcount reductions expected across a range of business areas, levels of seniority and offices worldwide, according to a reliable source.

 "Being a global leader requires that we continually re-assess our organization to look for ways to serve clients better, operate more efficiently, focus resources on strategic priorities and create new opportunities for our strongest employees," the firm said in the memo from President Rob Kapito and Chief Operating Officer Rob Goldstein.

The layoffs

are the largest ever for the $4.65 trillion money manager, which has about 13,000 employees globally.

Volatile markets over the past year have made business difficult for money management firms.  Of the top 10 U.S. companies by mutual fund and exchange-traded fund assets, all but one - Vanguard Group Inc. - saw those assets decline over the one-year period through February, according to Lipper, a fund data company. Industry analysts said several such companies had moved to cut staff.

BlackRock Chief Executive Larry Fink has highlighted as growth areas the firm's exchange-traded funds business, "alternatives" that include hedge funds, real estate and infrastructure investments, and so-called multi-asset strategies that invest across a range of asset classes.

The firm also conducted a round of job cuts in 2013, slashing 300 jobs. It ended that year with about 11,400 staff.

BlackRock isn't the only money manager to cut staff in recent months. Franklin Resources Inc. said in its most recent quarterly earnings that it would implement buyouts for about 300 of its 9,400 employees.