The US Secretary of State, Condoleezza Rice, has continued her diplomatic offensive against Iran.
The US says it is not just Iran's nuclear policy which is worrying
She has accused Tehran of being the central banker for terrorism around the world and working with Syria to destabilise the Middle East.
Ms Rice was testifying before the Senate Budget Committee in Washington.
On Wednesday, she announced that the US administration would request an extra $75m from Congress to promote democratic change inside Iran.
Condoleezza Rice said Washington had worked very hard to build an international coalition to confront what she described as Iran's aggressive policies, particularly its nuclear programme.
However, she stressed it was not just Tehran's nuclear policies which were concerning, but also what she described as its support for terrorism.
Iran, she alleged, was the central banker for terrorism around the world and was working with Syria to destabilise the Middle East.
Washington has long accused Tehran of trying to undermine the Middle East peace process and of interfering in countries like Iraq, charges Iran denies.
Ms Rice also again criticised Tehran's record on human rights and democracy.
At another Senate Committee hearing on Wednesday, she said the administration would ask Congress for an extra $75m to try to promote democratic change inside Iran, a policy which Iranian state radio dismissed as an outmoded diplomatic manoeuvre belonging to the Cold War era.
Nevertheless, it is Iran's nuclear programme which is currently attracting most international attention, ahead of a crucial meeting of the UN's nuclear watchdog on that issue early next month.
On Thursday, for the first time, France openly branded Iran's nuclear programme as a clandestine military project.