DUBAI/MOSCOW, Sept 22 (Reuters) - Iran has canceled import duties it imposed on wheat and barley in July, according to an official document seen by Reuters on Tuesday.

The document said the import duties ended on Sept. 6 for wheat and on Aug. 22 for barley. It gave no reason for the cancellation.

The Iranian government imposed a wheat duty of 1,500 rials per kilo, or about $45 to $50 a tonne, a level that rendered wheat imports commercially unfeasible.

The government had originally said the wheat duty would last for one year and the barley until Sept. 22.

The cancellation comes despite a statement by the government in August saying that it did not need to import wheat this year.

"Russian ships have not been offloaded in the previous two weeks, possibly because they were waiting for the tax to be removed soon. After they complete offloading and finish checks at the customs, one can expect a spike in export activity to Iran," a Russian industry source said.

Iran was the third largest buyer of Russian wheat last marketing year after Turkey and Egypt.

The import duties had applied to all private sector importers, traders and mills but not to the state import agencies Government Trading Corporation of Iran (GTC) or the State Livestock Affairs Logistic Co. (SLAL).

Iran, which was largely self-sufficient in wheat a decade ago, has emerged as one of the world's biggest importers. For the 2015/16 season, however, the USDA has forecast a drop in wheat imports to 4.0 million tonnes from 6.3 million a year earlier.

Iran is also the world's third largest importer of the animal feed barley, trailing Saudi Arabia and China. (Reporting by Bozorgmehr Sharafedin and Polina Devitt; Writing by Maha El Dahan; Editing by Dale Hudson and Louise Heavens)

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