Ayat Allah Ahmad Jannati, head of Iran's powerful supervisory body the Guardian Council, also applauded what he called a "slap in the face" given to Washington by the Islamic Republic.
Speaking to worshippers at Friday prayers in Tehran, Jannati said Iran was grateful for the foreign aid pouring in to help victims of last week's quake that killed at least 30,000 people.
The United States has sent scores of medics and tonnes of aid but, Jannati said, Iran would not tolerate any "meddling" after US officials expressed interest in better relations.
Washington broke ties with Iran in 1980 and last year dubbed it part of an international "axis of evil".
'Death to America'
"Naturally America wanted to take advantage of this situation by offering some help and bringing up the issue of relations," Jannati said.
"But it was given a slap in the face," he told worshippers to chants of "Death to America".
He was referring to Iranian President Muhammad Khatami, who on Tuesday said American aid was not a harbinger of better ties and noted US officials "talk a lot of nonsense".
Despite Khatami's comment, President George Bush on Wednesday ordered banking restrictions to be relaxed on Iran for 90 days to speed the flow of humanitarian relief to quake victims.
But Jannati, whose conservative views are closer to Supreme Leader Ayat Allah Ali Khamenei, said: "All their moves are political and now they offer help - politically."
Iran and the US have been at loggerheads since the Iranian revolution in 1979.
The US broke off relations over the storming of the United States Embassy in Tehran when approximately seventy Americans were taken captive.
Up to 50,000 people may have
died in the Bam earthquake
The US also accuses the Iranians of developing weapons of mass destruction.
On the other hand, there is still a lot of resentment in Iran over the CIA-orchestrated overthrow of the nation's democratically elected prime minister in 1953.
Iranians also condemn the US for supporting the Shah's brutal dictatorship, and bolstering Saddam Hussein during the Iran-Iraq war, during which one million people died.