The United States has imposed sanctions on the Syrian state-run oil company Sytrol for providing gasoline to Iran, a State Department spokesman said.

The new penalties come after the firm delivered $36 million worth of gasoline to Iran in April, department spokesman Patrick Ventrell said in a statement.

Sytrol was first put under U.S. sanctions last year.

Ventrell also criticized Tehran for its continuing support for the regime of Syrian President Bashar al-Assad. Assad has been fighting a 17-month-old uprising, during which activists claim moe than 20,000 people have been killed.

"Though these sanctions are a direct result of Syria's provision of gasoline to Iran, the United States views Iran's broader support for the Assad regime as completely unjustifiable," spokesman Ventrell said on Friday.

"Iran is actively advising, supplying, and assisting the Syrian security forces and regime-backed militias that are carrying out gross human rights abuses against the Syrian people. Iran is also providing the Assad regime with equipment to monitor opposition activity on the Internet."

The move comes as U.S. State secretary Hillary Clinton arrived in Turkey for talks with senior Turkish officials and Syrian opposition groups.

The State Department said it acted under the 1996 Iran Sanctions Act.

Washington and its allies say Iran is developing an atomic bomb, an accusation Tehran denies.

Earlier on Friday, the U.S. Treasury Department said it was extending sanctions against the Lebanese militant group Hezbollah for providing "training, advice and extensive logistical support" to the Syrian regime.

The group is designated as a terrorist organization by the United States.