WASHINGTON (REUTERS) - The United States is preparing to impose fresh sanctions on Iran's financial industry as soon as Thursday (Oct 8), a Republican congressional aide briefed on the matter said, as Washington ramps up pressure on Teheran weeks ahead of a key US election.

The move, which would effectively shut Iran out of the global financial sector, comes after the United States last month said it triggered a "snap back," or resumption, of virtually all UN sanctions on Iran, an assertion rejected by key European allies and most UN Security Council members including Russia and China.

The Washington Post first reported on the US plan.

Tensions between Washington and Teheran have soared since US President Donald Trump unilaterally withdrew in 2018 from the Iran nuclear deal struck by his predecessor and began reimposing sanctions that had been eased under the accord.

US sanctions have crippled the Iranian economy. President Hassan Rouhani in June said his country was experiencing the toughest year because of US economic pressure and the coronavirus pandemic, which has hit the Islamic Republic hard.

Iran hawks inside and outside the Trump administration have been pushing for the targeting of Iran's entire financial sector for some time.

Iran's oil exports, a key source of revenue for the Opec member, have dropped to their lowest levels in decades earlier this year, but Thursday's move, experts have said, could hit the Islamic Republic's ability to secure humanitarian goods such as medicine.

The US sanctions Mr Trump has reimposed target everything from oil sales to shipping and financial activities, and while they exempt food, medicine and other humanitarian supplies, many foreign banks are already deterred from doing business with the Islamic Republic - including humanitarian deals.