Oracle Corp said it plans to fire more workers mainly in Europe and Asia as it integrates Sun Microsystems, resulting in post-acquisition restructuring costs that will be more than triple what it previously disclosed.

The move underscores the challenges the world's No. 2 business software maker faces in turning around Sun, a money-losing hardware maker that it took over in January.

Oracle said on Friday in a filing with the U.S. Securities and Exchange Commission that it expected $675 million to $825 million in restructuring costs -- on top of the $325 million it previously disclosed.

It said the bulk of the job cuts and new costs associated with the restructuring would occur in Europe and Asia.

Oracle did not say in its filing how many jobs will be lost and company officials could not be reached for comment. As of January, Sun's workers accounted for about 20,000 of Oracle's 110,000 employees.

Oracle said that $550 million to $650 million of the additional costs would go toward employee severance, $85 million to $115 million would be related to facilities consolidation, and $40 million to $60 million would pay for contract terminations.

Oracle Chief Executive Larry Ellison said in January he intended to cut about 1,000 positions at Sun and hire 2,000 new employees for the division, most of them in sales.

Sun prospered in the 1990s by selling high-end computers at top dollar, then its business floundered with the collapse of the Internet boom and never fully recovered. The company is still widely respected for its technological prowess and the quality of its engineering staff.

Ellison said in an April interview that there was plenty of waste at Sun, which regularly sold products at a loss in a bid to goose revenue.

(Reporting by Jim Finkle; Editing by Gary Hill, Bernard Orr)