The US Senate has approved a bill to tighten¹ sanctions against Iran in a bid to force Tehran to abandon its nuclear programme.

美国参议院通过一项决议，加紧制裁伊朗以迫使塔利班放弃核计划。

The new sanctions will target Iran's Revolutionary Guard and investigate its role in the export of oil from the country.

It will also make it mandatory²（强制的） for US-listed firms to disclose any Iran-related business to the authorities.

The move comes ahead of crucial talks on Iran's nuclear programme.

"Today the US Senate put Iranian leaders on notice that they must halt all uranium enrichment activities or face another round of economic sanctions," Republican senator Mark Kirk, a co-author of the bill, said in a statement.

Increasing pressure

The US and its allies have been trying to force Tehran to abandon its nuclear programme, which they suspect Tehran is using to develop a nuclear weapon.

Last year, US President, Barack Obama, approved measures allowing the US to act against companies and foreign institutions that dealt with Iran's central bank.

The move was aimed at cutting Iran's oil revenues as its central bank is the principal clearing facility for payment for Iran's oil exports.

Earlier this year, the European Union announced an oil embargo³ against Iran.

The US has also been putting pressure on countries in Asia such as China, Japan, India and South Korea, which are among the biggest importers of Iranian oil to reduce their intake⁴ from Tehran.

Shortly after the bill was passed, one US lawmaker said that the move indicated US willingness to keep the pressure on Tehran.

"This bill is another tool that will demonstrate to Iran that the United States is not backing down," said Democratic senator Robert Menendez.