Almost a month after Iran signed an agreement with Russia's Gazprom for developing the Farzad-B gas field, the India-led consortium, which had discovered the gas reserves in the area, has made a $11-billion offer to the Iranians.

"We have given our best offer to them. Now, it is up to them to agree or not agree. We have told the Iranian authorities very clearly that some basic returns are necessary," news agency Bloomberg quoted Narendra Kumar Verma, managing director of ONGC Videsh, as saying.

ONGC Videsh is the overseas subsidiary of state-owned ONGC and leads the consortium that has two more public sector oil firms, Indian Oil Corp. and Oil India Ltd, as partners.

The $11-billion offer comprises $6 billion to be invested in developing the Farzad-B field and the rest on building a liquefied natural gas (LNG) export facility, the agency said, quoting Verma, with an offer to buy all the gas produced there.

The gas field has reported reserves of around 19 trillion cubic feet and is being seen as key to securing India's fast-rising LNG requirements. The consortium has been trying for the past eight years to secure developments rights for the gas field but sanctions imposed by Western powers on Iran scuttled India's efforts.

However, Iran's ambassador to India Gholamreza Ansari, in an interview to the BusinessLine in February this year, attributed the delay to "India's reservations".

"During the sanctions, especially, there was an exceptionally generous offer from Iran to India. But, as I said, because of the Indian reservations, it did not happen. Our preference is Indians, even our President was supportive. But, when it comes to technicalities, the issue of capabilities and financing comes," he had told the daily.

On June 7, the Economic Times had reported that Iran has finalised a deal with Gazprom to develop the gas field as a counter-response to India's attempts to exert pressure on the Iranian authorities to rush through the deal.

The Russian company also got two other fields, North Pars and Kish, along with Farzad-B, to develop as part of the agreement early last month.