DUBAI, Oct 21 (Reuters) - Oman has started marketing a two-part U.S. dollar bond issuance comprising seven and 12-year bonds, a document showed on Wednesday.

The Gulf state is marketing the seven-year paper in the 7% area and the 12-year in the 7.625% area, according to the document issued by one of the banks leading the deal.

Oman had announced on Monday plans to issue also a three-year tranche. (Reporting by Davide Barbuscia; Editing by Andrew Heavens)