DUBAI - Abu Dhabi National Oil Co (ADNOC) is expected to issue as early as this week a project bond in the region of $3 billion, in what would be the United Arab Emirates oil major's first public debt issue, sources familiar with the matter said on Tuesday.

The bond, with a maturity longer than 10 years, would be sold by one of ADNOC's subsidiaries, not by the holding company.

State-owned ADNOC, which manages almost all the proven oil reserves in the UAE, has mandated banks including Bank of Tokyo-Mitsubishi, First Abu Dhabi Bank, HSBC and JP Morgan to arrange the debt sale, said the sources.

"ADNOC is expanding its strategic partnership model and creating new investment opportunities across all areas of its value chain, as well as the more active management of its portfolio of assets," said an ADNOC spokesman when asked about the company's bond plans.

"Alongside this expanded partnership model, ADNOC is also taking a more active approach to optimising its capital structure to unlock value, free up capital, enhance returns and drive growth. ADNOC is therefore considering various options with regards to its ongoing financing strategy."

ADNOC's debt raising exercises are the latest sign of a change in the expansion strategies of energy companies in the Middle East, which are adjusting to an era of lower oil prices.

The company, which is also in the process of syndicating a $6 billion loan, is raising the financing as part of an overhaul of its capital structure which includes, among other things, the initial public offer of minority stakes in some of its operations.

ADNOC's group chief executive Sultan Ahmed al-Jaber said at a London conference on Tuesday that while the firm was considering an IPO of minority stakes in some services, it would remain wholly owned by the government of Abu Dhabi.

(Editing by Andrew Torchia) ((Davide.Barbuscia@thomsonreuters.com; +971522604297; Reuters Messaging: davide.barbuscia.reuters.com@reuters.net))