Century City-based Northrop Grumman Corp. said Sunday it agreed to sell its advisory services business TASC Inc. to private equity firm General Atlantic LLC and affiliates of Kohlberg Kravis Roberts & Co. for $1.65 billion in cash.

The No. 2 defense contractor says it will use the proceeds to fund a new $1.1 billion increase to its stock buyback program. At the end of the third quarter, the company had about $280 million remaining on its $2.5 billion share repurchase plan.

TASC, based in Chantilly, Va., serves intelligence, defense and civil agencies. The transaction is expected to close by the end of the year.