The United States on Thursday slapped fresh sanctions on Iran's financial sector, targeting 18 Iranian banks in an effort to further shut Iran out of the global banking system as Washington ramps up pressure on Tehran weeks ahead of the US election.

In an announcement posted on its website, the U.S. Treasury Department also identified the financial sector of the Iranian economy pursuant to Executive Order 13902, though it said the prohibitions did not apply to transactions for the provision of agricultural commodities, food, medicine or medical devices to Iran.