DUBAI/ABU DHABI, Oct 6 (Reuters) - National Bank of Abu Dhabi is finalising plans to issue a conventional bond of at least benchmark size, sources familiar with the plans told Reuters on Thursday.

NBAD has mandated banks to arrange the issue and is in the process of organising an investor roadshow, one of the sources said, declining to name the banks. Benchmark is commonly understood to mean at least $500 million.

There was no immediate official comment from NBAD.

Last month, NBAD indefinitely postponed the region's first issue of a "green bond", whose proceeds were to have been used to invest in renewable energy projects; investors considered the pricing unattractive, banking sources said.

(Reporting by Tom Arnold and Stanley Carvalho; Editing by Andrew Torchia) ((Tom.Arnold@thomsonreuters.com; +97144536265; Reuters Messaging: tom.arnold.thomsonreuters.com@reuters.net))