The US Treasury blacklisted Friday a key Iranian businessman and five others whom it said were trying to help Iran circumvent international sanctions to export oil.

The Treasury identified a Seyed Seyyedi, the director of Sima General Trading, as a key player in the network that includes Greek shipowner Dimitris Cambis, the National Iranian Oil Company (NIOC) and the Naftiran Intertrade Company Sarl (NICO).

Seyyedi, it said, controls a number of companies in the United Arab Emirates that have been "used by him to assist NICO and NICO front companies, such as Sima General Trading, in its sanctions evasion schemes."

The others blacklisted, four Iranians and one Iran-born British citizen who work for NICO and NIOC-linked firms, were named as helping Tehran in its efforts to beat sanctions.

"In its efforts to evade sanctions, the government of Iran relies on front companies, financial institutions and businessmen willing to engage in deceptive transactions to conceal the direct involvement of the Iranian government and its instrumentalities," the Treasury said in a statement.

The US and the international community have placed tight controls on Iran's ability to export oil and other avenues of earning foreign exchange to press it to give up its alleged efforts to build a nuclear weapon.

"Our sanctions on Iran's oil sales are a critically important component of maintaining pressure on the Iranian government, and we will not allow Iran to relieve that pressure through evasion and circumvention," said Treasury Under Secretary for Terrorism and Financial Intelligence, David Cohen.

The Treasury sanctions on the individuals and companies freezes any of their assets under US jurisdiction and forbids Americans from doing business with them.