Bloomberg | Saket Sundria & Debjit Chakraborty:� An Indian consortium is willing to spend as much as $11 billion to develop a giant Iranian natural gas field and build the infrastructure to export the fuel as long as the Persian Gulf nation guarantees a �reasonable return� on the project, according to the company leading the group.

ONGC�Videsh Ltd.�has offered to invest as much as $6 billion on the Farzad-B field and spend the remaining amount to build a liquefied natural gas export facility, according to Narendra Kumar Verma, managing director of the overseas investment unit of India�s largest explorer,�Oil & Natural Gas Corp.�The group is seeking a return of about 18 percent, and Indian companies are willing to buy all the gas exported from the project, Verma said.

�We have given our best offer to them.�Now, it is up to them to agree or not agree,� Verma said in a phone interview. �We have told the Iranian authorities very clearly that some basic returns are necessary.�

As India,�the�world�s fourth-largest LNG�buyer, seeks to lock up gas resources to meet growing demand and spur the use of�cleaner-burning fuels, Iran is emerging from sanctions that stifled investment in its energy sector. The Persian Gulf nation on Monday�plans to sign�a formal contract with�Total SA�and�China National Petroleum Corp.�to develop its share of the�offshore South Pars project, the world�s biggest natural gas field.

Officials from Iran�s Ministry of Petroleum and the National Iranian Oil Co. were unable to comment Sunday on Farzad-B. Iranian Deputy Oil Minister Amir Hossein Zamaninia said last month�discussions�with the Indian side on Farzad-B were continuing and have �very much advanced.� Iran was also in discussions with Russia�s�Gazprom PJSCon the Farzad fields, he said.

The two countries had aimed to�conclude�a deal�by February on developing the field, which India has said holds reserves of almost 19 trillion cubic feet. The consortium, which includes�Indian Oil Corp.�and�Oil India Ltd., has been trying to secure development rights to the Farzad-B gas field�since�at least 2009.

Delay Damage

The delay over a final outcome has started hurting oil trade between the two countries. India, which bought Iranian crude even during the years of U.S.-led sanctions against Tehran, has recently�reduced purchases,�leading to the withdrawal by Iran of�some benefits�on sales in retaliation, Bloomberg reported in April.

�We are ready to invest,� Verma said. �Ultimately, that�s positive for them.�

The South Asian nation is promoting the cleaner-burning fuel to curb the use of more polluting alternatives such as coal and petroleum coke, an oil-refining byproduct, to meet its pledge of slashing�emissions�by a third by 2030.

ONGC Videsh and Indian Oil each own�40 percent�interest in the Farsi block that holds Farzad-B field, while Oil India has�20 percent.