The United States on Friday imposed sanctions on Iran's petrochemical industry, vowing to target more of the Islamic regime's sources of revenue after curbing its vital oil exports.

Washington also announced action against companies based in Cyprus, Kyrgyzstan, Ukraine and the United Arab Emirates for support to Iranian entities accused of involvement in the country's controversial nuclear program.

US officials said they were taking action against Iran's petrochemical industry as it represented the Iranian government's largest source of revenue after oil, which has been severely curtailed by a US-led sanctions campaign.

"We are committed to intensifying the pressure against Iran, not only by adopting new sanctions, but also by actively enforcing our sanctions and preventing sanctions evasion," David Cohen, the Treasury Department point man on sanctions, said in a statement.

"We will continue to work with our partners around the world to ensure that the sanctions pressure on Iran builds so long as Iran continues to defy its... international obligations," he said.

The United States slapped sanctions that include a ban on US-based financial transactions on the Niksima Food & Beverage Co., a Dubai-based frozen yogurt and dessert company.

The State Department accused the company of receiving payments on behalf of Iran's Jam Petrochemical Company, which was put under the same sanctions.

The Treasury Department also identified eight Iranian petrochemical companies as being under the control of the Tehran government, which subjects them to US sanctions.

The United States, Israel and European nations have demanded that Iran end sensitive uranium work, fearing that it could be used to develop a nuclear bomb. Iran insists its nuclear program is for peaceful purposes.

Since last year, the United States has brandished sanctions against anyone who buys Iran's oil. In its latest move, it punished Ferland Co., which is based in Cyprus and Ukraine, for allegedly assisting the Iranian National Tanker Company.

US authorities also took action against several individuals and airlines for alleged cooperation with Iran, including Kyrgyzstan-based Kyrgyz Trans Avia and Ukraine-based Ukrainian-Mediterranean Airlines, also known as Um Air.

Despite the tough sanctions, the United States on Thursday lifted a ban on laptops, mobile telephones and other equipment, saying the step would help ordinary Iranians circumvent government controls.