Saudi oil giant Aramco is in advanced talks to buy a stake in India's Reliance Industries Ltd.’s (RIL) oil refining and chemicals business, according to Bloomberg, which cited people with knowledge of the matter.

Saudi Aramco is in talks for an all-stock deal to acquire a nearly 20 percent stake in the Reliance unit for about $20 billion to $25 billion in Aramco’s shares, Bloomberg reported. Last week, Aramco said that it was conducting due diligence on the deal. A deal could be expected in the coming weeks, the report said.

Reliance had announced a sale of a 20 percent stake in its oil-to-chemicals business to Aramco for $15 billion in 2019. However, the deal fell through after oil prices and demand crashed last year due to COVID-19.

If the deal works out, Reliance, which is headed by billionaire Mukesh Ambani, will get a steady supply of crude oil for its refineries and a stake in Saudi Aramco.

"Based on Aramco’s market valuation of about $1.9 trillion, a transaction would give Reliance a stake of around 1 percent in the world’s biggest energy company," the Bloomberg report said.

In June, RIL said it hoped to formalise its partnership with Saudi Aramco this year when Saudi Aramco's Chairman Yasir Al-Rumayyan joined the Indian conglomerate's board as an independent director.

"Our oil-to-chemicals biz faced unprecedented challenges by severe economic contraction at the beginning of the year. Yet we were probably the only company globally that operated at near full capacity and was profitable in every quarter," Business Standard quoted Ambani as saying in June.

"Continued engagement and resolve from both sides, even during this pandemic, is a testimony of strong relationship between Saudi Aramco and Reliance. I expect our partnership to be formalised in an expeditious manner this year," he added.