Oman's Bank Dhofar is working with National Bank of Abu Dhabi and Standard Chartered as it studies options for raising its reserves including selling a capital-boosting bond, banking sources told Reuters on Tuesday.

The sultanate's second-largest lender by assets said last month it was mulling options for raising up to $300 million of capital at the earliest opportunity, with a bond which enhanced its Tier 1, or core, capital the preferred method.

The two advisers have been working with Bank Dhofar for around six months, one of the banking sources said, speaking on condition of anonymity as the information isn't public.

Calls to Bank Dhofar's chief executive, its chief financial officer and a spokesman all went unanswered.

A number of Gulf banks, including Qatar's Doha Bank and Abu Dhabi Islamic Bank, have said in recent weeks they are planning to boost their capital reserves after a period of strong growth.

Many are looking at the bond or sukuk route, although should Bank Dhofar complete such a transaction it would be the first by an Omani lender. The sultanate's central bank has yet to clarify how such instruments would be treated under Basel III regulations, which is impacting on Bank Dhofar's thinking, it said last month.

Another potential complication is the possible merger with Bank Sohar, which Bank Dhofar first approached its smaller rival about in July 2013 but has yet to come to any formal conclusion.

A second banker said such uncertainty would play on investors' minds when they were conducting due diligence.

Bank Dhofar had a total capital adequacy ratio (CAR), a key indicator of a bank's financial health, of 13.82 per cent at the end of 2014, down from 14.09 per cent at the same point of the previous year.

By comparison, Bank Muscat and National Bank of Oman, the sultanate's largest and third-largest lenders by assets, had respective CARs at the end of 2014 of 15.92 per cent and 14.6 per cent. – Reuters