Saudi Arabia plans to list 1 per cent of the state oil giant - the world's largest oil company.

Saudi Aramco has hired nine banks as joint global coordinators to lead its planned initial public offering (IPO), slated to be the world's largest, two sources familiar with the matter told Reuters on Wednesday.

The mandates have been heavily sought by the world's biggest investment banks for a transaction which, according to Saudi Crown Prince Mohammed bin Salman's initial plans, could generate around $100 billion for Saudi Arabia's state coffers.

The kingdom plans to list 1 per cent of the state oil giant - the world's largest oil company - on the Riyadh stock exchange before the end of this year and another 1 per cent in 2020, sources told Reuters this week, as initial steps ahead of a public sale of around 5 per cent of Aramco.

Aramco has selected JPMorgan Chase & Co , Morgan Stanley and Saudi Arabia's National Commercial Bank, which were previously working on the share sale before it was paused last year, the sources said, declining to be identified due to commercial sensitivities.

It has also chosen Bank of America Merrill Lynch, Goldman Sachs Group Inc , Credit Suisse Group AG, Citigroup Inc, HSBC Holdings PLC and Saudi Arabia's Samba Financial Group, they added.

To secure the lead role on the IPO, JPMorgan's efforts were led by senior bankers in New York, London and Saudi Arabia who had long-standing relationships in Saudi Arabia, rather than Chief Executive Jamie Dimon, according to a person familiar with the matter.

Aramco, JPMorgan, Bank of America, Citi, Credit Suisse, Goldman Sachs and HSBC declined to comment. The remaining banks did not immediately respond to requests for comment.

The IPO plan has rapidly gained momentum in recent days with the appointment of the head of the kingdom's PIF sovereign wealth fund, Yasser al-Rumayyan, as Aramco's new chairman.

Mr Rumayyan, a close ally of Prince Mohammed, took over from former energy minister Khalid al-Falih in a move to separate Aramco from the ministry, a step Saudi officials have said was important to pave the way for the IPO.

Bankers have been courting Saudi Arabia to secure roles in the transaction, which has faced repeated delays, but which officials have said will happen by 2020-2021.

Aramco's chief executive, Amin Nasser, said this week that the domestic IPO would be the "primary" listing but that the company was also ready for an international share sale. He said the final decision on venue and timing rested with the government.

The flotation is crucial for Prince Mohammed's plans to diversify the Saudi economy in an era of low oil prices.

Based on the indicated $2 trillion valuation that Saudi Aramco had hoped to achieve, a 1 per cent float would be worth $20 billion, a huge milestone for the local stock market.

Analysts and bankers, however, have said $1.5 trillion is a more achievable valuation for Aramco.

Aramco raised $12 billion this year in its first international bond, gaining more than $100 billion in demand, in a deal that many saw as a pre-IPO relationship-building exercise with international investors.