UPDATE 1-ONGC, PetroVietnam to bid for BP asset-India oil min

* Indian state-run ONGC, PetroVietnam mulling joint bid

* India oil min says Vietnam PM agrees to proposal

* India oil min says will have to negotiate deal with BP (Adds background)

NEW DELHI, July 22 (Reuters) - Indian state-run explorer Oil and Natural Gas Corp (ONGC.BO: Quote) and PetroVietnam are considering a joint bid for BP's (BP.L: Quote) stake in an offshore Vietnam gas field, Indian Oil Minister Murli Deora told Reuters on Thursday.

ONGC has a 45 percent share in Block 6.1 in the Nam Con Son basin, off Vietnam's southeast coast, which is operated by BP with a 35 percent stake, ONGC's website shows. The rest is owned by PetroVietnam.

"Just now I have met the Vietnam prime minister. In principle, he has agreed to our proposal. Now we have to negotiate with BP," Deora said.

On Wednesday, ONGC head R.S. Sharma said the company was interested in buying BP's stake in the project. [ID:nSGE66K0I0]

A BP spokesman said the company was "exploring divestment options" for its interest in the Nam Con Son gas project, which the London-based firm says is one of Vietnam's largest foreign investment projects.

The interest, which comprises stakes in the Lan Tay and Lan Do gas fields, the Nam Con Son pipeline and the Phu My power generation project, is worth $966 million, analysts at UBS said in a research note on Monday. (Reporting by Nidhi Verma; Editing by Ranjit Gangadharan)