MUMBAI - U.S. drug firm Pfizer has approached several Indian drugmakers for possible alliances to bolster its revenues, the Economic Times reported on Friday.

Pfizer has tapped Cadila Healthcare , Emcure, Intas Pharma and Mankind Pharma, but the Indian companies have not responded favourably to the offers, the report said citing an unidentified senior industry executive with direct knowledge of the matter.

"Pfizer approached Mankind Pharma with a lucrative offer, valuing the India company at $1 billion," the report quoted another person familiar with the matter as saying.

Mankind's founder and managing director R. C. Juneja, however, denied that any multinational firm had approached it with an offer, the report said.

Intas and Cadila did not respond to emailed queries from the paper and Emcure officials could not be contacted, it said.

A spokeswoman for Pfizer Ltd when contacted by Reuters said, "We do not comment on rumours or speculation." Some of Pfizer's popular products are set to go off-patent in the next three years, exposing it to competition from cheaper copycat versions, the report said.