"We are witnessing, in Iran, a horrible human tragedy. You've got a government there that has been seen crushing its people in the streets of Tehran," Republican Representative Eric Cantor told AFP.
"How do you expect to trust, to engage with, a regime like that? How could we ever tolerate a regime like that having nuclear weapons?" said Cantor, the number two Republican in the House of Representatives.
Cantor said the US Congress should quickly pass legislation aimed at choking off Iran's gasoline imports and foreign investments in its energy sector to break its defiance of global demands to freeze its suspect nuclear program.
"We can send a message very quickly to our allies and the rest of the world that we mean to live by our commitments that we do not want Iran to become a nuclear power," said the lawmaker, whose home state is Virginia.
US efforts to keep Iran from developing nuclear weapons must hold firm whether or not Iranian President Mahmoud Ahmadinejad ultimately prevails in his disputed electoral bout with rival Mir Hossein Mousavi, said Cantor.
"It's very clear that democracy in Iran is somewhat of a mystery and that clearly the clerics in that country are the ones that control the levers of power. And our policy vis-a-vis Iran needs to reflect that reality," he said.
Cantor also said the Obama administration had not sufficiently criticized the official crackdown on protests by Mousavi supporters.
"Their silence on the issue of human rights violations is very troubling to me. America has a moral responsibility to stand up for human rights around the world and to condemn the abuses that are occurring in Tehran today," he said.
Obama has said he is "deeply troubled" by the violence in Iran, but that Washington cannot be seen as "meddling" in the Islamic Republic's affairs, and said that he will continue his policy of reaching out to Tehran.
