"(This is) the biggest foreign investment in the history of Reliance," Mr Ambani said.

Highlights RIL will sell a 20% stake in its petrochemical business to Saudi Aramco

Saudi Aramco will supply 500,000 barrels a day of crude oil to RIL

Saudi Aramco is the world's biggest oil producer

Reliance Industries Ltd is set to sell a 20 per cent stake in its oil to chemicals business to Saudi Aramco in one of the largest foreign investments in the country, Reliance Chairman Mukesh Ambani said on Monday.

"(This is) the biggest foreign investment in the history of Reliance," Mr Ambani said at the company's annual general meeting in Mumbai.

"It is also amongst the largest foreign investments ever in India."

The deal valued the business at $75 billion including debt, he said.

Saudi Aramco, the world's biggest oil producer, has been in talks with Reliance on the stake sale as it plans to secure new markets for its crude.

Saudi Aramco will also supply 500,000 barrels a day of crude oil on a long-term basis to RIL's Jamnagar refinery, Mr Ambani said.

"This signifies perfect synergy between the world's largest oil producer and the world's largest integrated refinery and petrochemicals complex," he added.

The partnership will cover all of Reliance's refining and petrochemical assets, including its 51 per cent stake in the petroleum retail joint venture, he said.

Last week, Reliance announced that it was forming a fuel retailing joint venture with global oil major BP in which Reliance would own a 51 per cent stake.