The United States on Tuesday added a Belarussian oil company to its blacklist of firms accused of flouting sanctions imposed on Iran for failing to rein in its suspect nuclear program.

Belarusneft allegedly signed a $500 million dollar contract in 2007 with the Iranian firm NaftIran Intertrade to develop the Jofeir oil field.

NaftIran was slapped in September 2010 with US sanctions as part of a UN embargo imposed on Tehran in June 2010.

The blacklisting of Belarusneft means the firm will be barred from doing business on the American market, a State Department statement said.

According to the US State Department, the global sanctions have hit Iran's capability to invest in oil and gas production.

"Iran's ability to attract new investment to develop its oil and natural gas resources, and to produce or import refined petroleum products, has been severely limited," the State Department said in a statement.

Cutting the Islamic republic's income from oil and gas revenue is one of the main thrusts of the US strategy to stop Iran from investing in its nuclear energy program.

Western nations accuse Iran of covertly seeking to acquire an atomic bomb. But Tehran has denied the allegations, saying its nuclear program is only for civilian purposes.