UPDATE 1-Cairn India to supply crude oil to Reliance Ind

* Cairn agrees to sell Managal crude to Reliance

* Deal covers 1.92 mln bbls, source says

* Crude to sell at 10-15 percent discount to Brent

MUMBAI, Nov 4 (Reuters) - Cairn India (CAIL.BO: Quote, Profile, Research), a unit of UK firm Cairn Energy (CNE.L: Quote, Profile, Research), said on Wednesday it had reached a deal to supply crude oil from its field in western India to leading conglomerate Reliance Industries (RELI.BO: Quote, Profile, Research).

Cairn will deliver the oil, from its Mangala field in the state of Rajasthan, to Reliance's refinery in Jamnagar in the western state of Gujarat.

Financial details were not disclosed.

A source close to the negotiations said Cairn would be supplying about 1.92 million barrels to Reliance until March 31.

"First parcel from Rajasthan terminal to Reliance's refinery is expected to be sent by trucks on Nov 24," the source, who did not wish to be named told Reuters