India's Oil and Natural Gas Corporation (ONGC) and the Hinduja Group will meet again with Iranian firms on developing an oil and a gas field in Iran and downstream projects in India.

Officials from ONGC Videsh, the overseas arm of state-run ONGC, and Hinduja's Ashok Leyland Project Services met officials of Iran's state-run Petropras and Naft Iran Intertrade Company (Nico), a subsidiary of National Iranian Oil Company.

Hinduja Group India executive vice-chairman Subir Raha said the upstream and downstream projects could cost $20 billion.

"This is the ballpark number at current prices. But the exact number will be known after a detailed feasibility report," he said.

"Negotiations will continue, we will meet shortly," said Raha.

An ONGC official said that no agreement has been signed on the Indian firms' participation in the Iranian projects, but a basic understanding on some issues has been reached.

"There are still some open issues. We are moving ahead. Commercial issues have yet to be worked out," said the ONGC official.

The two sides have yet to finalise gas pricing, project cost and supply commitment from Iran.

ONGC and Hinduja Group are looking at joining the development of the South Pars Phase 12 gasfield and the Azadegan oil field in Iran.

ONGC has offered the Iranian firms an equity stake in its proposed refinery and a liquefied natural gas terminal in southern India, which Hinduja Group will also be involved in.

ONGC plans to build a 300,000 barrels per day refinery in Andhra Pradesh state, and a 7.5 million tonnes per year LNG terminal in Karnataka state, sources said. -Reuters