The rating is the first assigned to ADNOC, one of the world's largest oil producers by volume, and will allow the company wider access to international financial markets and investors.

ADNOC's rating "reflects the company's high upstream output coupled with low production costs, significant reserves, downstream integration and a conservative financial profile," Fitch said in a statement.

Fitch also cited ADNOC's geological diversification of onshore and offshore reserves, as well as the company's low leverage and its "flexible dividend policy," meaning that it has no obligation to pay out a certain proportion of earnings or a fixed amount.

"Today's announcement by Fitch ... recognises ADNOC's world-class resources, our strong operating and financial performance, our robust financial profile and our disciplined investment model," Sultan al Jaber, UAE Minister of State and ADNOC Group CEO, said in a statement.

ADNOC has undergone major change since al-Jaber's appointment in 2016, part of wider economic reforms led by Abu Dhabi Crown Prince Sheikh Mohammed bin Zayed Al Nahyan.

The firm has started privatising its services businesses, ventured into oil trading and expanded partnerships with strategic investors.

"While ADNOC has no plans to issue a bond at the Group holding level, these credit ratings will enable greater access to a more international investor base and provide ADNOC with further smart financing options," ADNOC said.

In 2017, ADNOC borrowed billions of dollars in the international capital markets as part of an overhaul of its capital structure.

The Abu Dhabi Crude Oil Pipeline, a company controlled by ADNOC, in the same year issued a debut bond of around $3 billion which was rated AA by Fitch and S&P.