DUBAI, May 31 (Reuters) - Saudi British Bank (SABB), which is 40 percent owned by HSBC Holdings, has appointed Goldman Sachs GS.N to advise it on a proposed merger with fellow Saudi Arabian lender Alawwal Bank, sources familiar with the matter said.

SABB and Alawwal said on April 25 they had agreed to start talks on a merger that could create the kingdom's third biggest bank with assets of nearly $80 billion.

SABB and Goldman Sachs declined to comment on Wednesday.

Alawwal Bank, which is 40 percent owned by Royal Bank of Scotland, selected JPMorgan as its adviser on the deal, Reuters reported on May 29.

(Reporting By Tom Arnold and Saeed Azhar) ((Tom.Arnold@thomsonreuters.com; +97144536265; Reuters Messaging: tom.arnold.thomsonreuters.com@reuters.net))