"We can clearly detect a turning point in the policy of the Americans," Hossein Mussavian, spokesman for Iran's nuclear negotiating team, told state television in Tehran on Thursday.
"The United States is in the process of revising its past policies. They will probably accept the European request to show more flexibility and support the negotiations process launched with Iran," he said.
Iran, which is negotiating with the European Union over its nuclear activities, says the programme is only for peaceful energy purposes and has denied any plans to build the bomb as alleged by the United States.
A senior State Department official said the US had promised an early answer to new European proposals for persuading Iran to renounce suspect nuclear activities.
The IAEA has asked Iran to
cooperate with N-inspectors
The official said US Secretary of State Condoleezza Rice discussed the next steps towards Iran with her German, British and French counterparts on Tuesday in London.
The US, which had initially kept a distance from the negotiations between the EU-3 and Iran, on Monday signaled it was now studying ways of boosting its support.
Among the EU incentives reportedly under consideration were support for Iranian membership in the World Trade Organisation and an offer to help Tehran procure spare parts for its ageing fleet of passenger planes.
"The United States could lift its opposition to the benefits which the Europeans would grant Iran and which need the accord of the Americans," according to Mussavian.
He said the US did not want "to be blamed for a failure in the negotiations between the Europeans and Iran... We will probably see a change in US policy within one or two months".
"The United States is in the process of revising its past policies"
Iran nuclear team spokesman
Britain, France and Germany have been negotiating since December with Iran to secure guarantees that the Islamic republic restricts itself to peaceful uses of nuclear energy.
Meanwhile in Vienna, the 35 nations on the board of the International Atomic Energy Agency (IAEA) on Thursday urged Iran to step up cooperation with UN inspectors and backed a EU offer of incentives if Tehran ends sensitive nuclear work.
Earlier this week, the head of the IAEA, Muhammad al-Baradai, said by concealing parts of its nuclear programme for nearly two decades Iran had created a "confidence deficit" and urged Tehran to improve its transparency and cooperation with UN inspectors.