NEW YORK, June 24 (Reuters) - Cigna ( CI ) sued Bristol

Myers on Tuesday, accusing the drugmaker of violating

federal antitrust law by maintaining a monopoly over a

blockbuster multiple myeloma drug sold under the brand name

Pomalyst.

The insurer said Bristol Myers and its Celgene unit have

delayed generic versions of Pomalyst from entering the market,

causing Cigna ( CI ) and other purchasers to overpay by hundreds of

millions, and perhaps billions, of dollars.

Cigna ( CI ) filed its lawsuit in Manhattan federal court.

(Reporting by Jonathan Stempel in New York)