Indonesia said its rupiah currency would strengthen going forward due to easing global financial market uncertainties and the country's new earnings retention rule, its finance minister said on Tuesday.

Under a rule introduced last month to bolster domestic U.S. dollar supply, which comes into force Aug. 1, natural resource exporters must retain 30% of their proceeds for every custom document for exports worth at least $250,000 in the domestic financial system for three months. (Reporting by Stefanno Sulaiman; Writing by Stanley Widianto; Editing by Christina Fincher)