US exports to Iran have jumped by nearly a third this year, despite the tightening of financial sanctions.

According to the US Census Bureau, exports to Iran rose by 32 per cent to $199.5m in the first eight months of 2012, from $150.8m during the same period last year.

The largest category of US exports through August was $89.2m in sales of wheat and other grains. In 2011, the US sold $21m worth of corn to Iran.

Sales of dairy products and other related exports more than doubled to reach $20.3m from $7.8m.