"I congratulate... Yasir al-Rumayyan, governor of the Public Investment Fund, on his appointment as chairman of the board of directors of Saudi Aramco, which is an important step to prepare the company for the public offering," Khalid al-Falih said on Twitter.

Rumayyan, already an Aramco board member, is the head of the vast Saudi sovereign wealth fund that is spearheading an ambitious plan to diversify the kingdom's oil-reliant economy.

The news comes after Falih, who has long headed both Aramco and the energy ministry, last week lost another portfolio.

Saudi Arabia on Friday announced the creation of a new ministry of industry and mineral resources, separating it from the energy ministry.

Aramco has said it plans to float around five percent of the state-owned company in 2020 or 2021, in what could potentially be the world's biggest stock sale.

The planned IPO forms the cornerstone of a reform programme envisaged by Crown Prince Mohammed bin Salman to wean the Saudi economy off its reliance on oil.

It aims to raise up to $100 billion based on a $2 trillion valuation of the company -- although investors have long debated whether Aramco is really worth that much.

Failure to reach a $2 trillion valuation as desired by Saudi rulers is widely considered the reason the IPO, earlier scheduled for 2018, has been delayed.

Earlier this month, Aramco said its first half net income for 2019 slipped nearly 12 percent to $46.9 billion on lower crude prices.

It was the first time the company has published half-year financial results, and comes after Aramco opened its secretive accounts for the first time in April, revealing itself to be the world's most profitable company.