Bank of New York will begin performing securities portfolio accounting next year for most of the $321 billion that J.P. Morgan & Co. manages, the companies said Thursday.

European and Asian private client accounts are excluded from the arrangement. Bank of New York already provided services to J.P. Morgan's asset management group, including custody.

J.P. Morgan has conducted securities portfolio accounting-inventory management, market valuation, and accounting-internally with separate systems.

"What we realized is a single, integrated platform was going to be the best way to go," a J.P. Morgan spokeswoman said. "At our core we are an investment management firm. This is not our area of expertise, the way it is the Bank of New York's."

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