Saudi Aramco, the state-controlled oil and gas giant, has selected investment bank Moelis & Co as an adviser to help it execute, what is expected to be the world’s biggest ever initial public offering (IPO).

Moelis, a New York-based boutique firm has been hired as internal independent adviser, as part of a team, tasked with preparing for the share sale, according to media reports. Moelis joins JPMorgan and Michael Klein, an investment banker who runs his own advisory firm, who have already been selected to work on the transaction.

Aramco earlier in January also asked banks including US-based Goldman Sachs and Morgan Stanley, the UK’s HSBC and Credit Suisse to pitch for advisory roles on the IPO. A decision is expected soon on appointing international and local banks for preparatory work.

Aramco, which has been the main revenue-earner for Saudi Arabia over the past eight decades, is targeting the second half of the 2018 for its IPO and will award formal mandates later this year.

Moelis’s appointment is a big win for the bank, which was founded by veteran US dealmaker Ken Moelis in 2007. The bank has an experienced team of advisers and advised the Dubai government on its $25bn debt restructuring of conglomerate Dubai World in 2011. Reports said a Moelis spokesperson declined to comment and Aramco was not immediately available to comment.

Riyadh aims to list less than 5 per cent of Aramco, which is estimated to be valued at more than $2 trillion. The $100bn in proceeds from the share sale would make it the biggest IPO in the world, dwarfing the $25bn raised by Chinese internet retailer Alibaba in 2014.

Aramco CEO Amin Nasser said in October that the oil and gas giant will “very soon” announce a list of investment banks and consultants for the IPO. The public offering would cover Aramco’s entire business and not just distribution and refining operations, he said at the time.

Saudi Arabia aims to list the company on the Saudi Stock Exchange (Tadawul) and one or two as yet unnamed international bourses.

Aramco is at the heart of Saudi Arabia’s economic diversification plan, which includes the privatisation of state assets. The measures include reducing subsidies, introducing taxes, spending cuts and increasing and introducing new fees on government services to generate alternative revenue lines.