But mindful of the situation in Iraq, lawmakers warned that nothing in this document should be "construed as authorising the use of force against Iran."

Although it does not name any countries by name, the measure is seen as a clear warning to Russia and China, two key members of the UN Security Council that have been resisting calls for new international sanctions against Tehran in response to its refusal to halt uranium enrichment.

Russia has been involved in a 800-million-dollar project to help Iran build a nuclear power plant in Bushehr and has been selling it modern weaponry, while China has been accused of supplying the Islamic republic with advanced missile technology.

The bill that passed by the Senate in pre-dawn hours by voice vote and cleared the House of Representatives a day earlier came as Iran and the European Union are engaged in delicate negotiations designed to persuade Iran to halt its enrichment work and avoid a major international showdown.

US Secretary of State Condoleezza Rice was expected to confer with EU foreign policy coordinator Javier Solana and her counterparts from Britain, China, France, Germany and Russia over the weekend to take stock of progress reached in these talks.

Following the carrot-and-stick approach adopted by Washington, the Iran Freedom Support Act states that it should be the policy of the United States "not to bring into force an agreement for cooperation with the government of any country that is assisting the nuclear programme of Iran or transferring advanced conventional weapons or missiles."

The measure calls for this policy to remain in effect until Iran has suspended all enrichment-related activities, committed to verifiably and permanently refrain from such nuclear work in the future or the targeted country has severed ties with its Iranian partners.

The president has been granted the right to waive provisions of the bill, if he finds that US national security interests warrant it.

The bill also authorises the president to provide financial and political assistance to foreign and Iranian individuals and organisations that promote democracy for Iran.