India billionaire Mukesh Ambani's Reliance Industries Ltd. is offering to sell a $20 billion stake in its retail business to Amazon.com Inc., reports said this week.

Quoting a person with knowledge of the matter the reports said Amazon had held discussions about investing in the conglomerate's Reliance Retail Ventures Ltd., the person said.

Reliance Industries is willing to sell as much as a 40% stake in the subsidiary to Amazon, the person said, asking not to be identified because the information is private.

At $20 billion, the deal would be the biggest ever in India as well as for Amazon, according to data compiled by Bloomberg.

Shares of Reliance Industries extended gains and touched an all-time high after the reports were published. Shares in Reliance were up almost 9 percent Thursday, making it the first listed company in India to attain a market capitalization of over $200 billion.

Reliance would provide a brick-and-mortar component to Amazon's ambitions in a country where online purchasing still accounts for a minuscule share of an estimated $1 trillion retail market, the reports said.

Amazon hasn't made any final decision on the size of its potential investment, and talks could still fall apart, the person said. A representative for Amazon declined to comment.

The Seattle-based retail empire is reported to have shown interest with RRV over a potential 40 percent stake in the business, Bloomberg said. The two companies have been talking since this summer when reports came out that Amazon was considering snagging a 10 percent ownership of RRV.

Reliance currently has nearly 12,000 brick and mortar shops scattered across the country. It operates a chain of supermarkets, the country's biggest network of consumer electronics, clothing shops, and the popular online grocery shop JioMart that both Facebook and Alphabet have a stake in.

Abu Dhabi's state fund Mubadala Investment Co and Saudi Arabia's Public Investment Fund - both investors of Jio Platforms - are also examining a potential share acquisition, reports said.

Shares of Reliance Industries have been in demand this week with another statement detailing a $1 billion investment from Silver Lake Partners. Reports said  Reliance Retail Ventures is set to draw additional investments worth $5 billion from KKR and Co., Mubadala Investment Co. and Abu Dhabi Investment Authority.

California-based private equity fund Silver Lake, an investor in Reliance Industries Ltd's Jio Platforms unit, has picked up a 1.75% stake in Reliance Retail Ventures valuing the company at $57 billion.

In May, Reliance launched online grocery service JioMart. It has been aggressively building its retail presence through acquisitions, moving beyond its core oil and gas business.