US President Barack Obama said that the United States would offer arch-foe Iran an extended hand of diplomacy if the Islamic Republic''s leaders "unclenched their fist."

Obama said he would in the next few months lay out a general framework of policy towards Tehran in an interview with Dubai-based Al-Arabiya satellite television network, a week after his historic swearing-in as president.

"As I said in my inauguration speech, if countries like Iran are willing to unclench their fist, they will find an extended hand from us."

"It is very important for us to make sure that we are using all the tools of US power, including diplomacy, in our relationship with Iran," Obama said.

Earlier, Susan Rice, the new US ambassador to the United Nations made her debut and pledged vigorous" and "direct" nuclear diplomacy with Iran but warned of increased pressure if Tehran refuses to halt uranium enrichment.

"We will look at what is necessary and appropriate with respect to maintaining pressure toward that goal of ending Iran''s nuclear program," she added.

"Dialogue and diplomacy must go hand in hand with a very firm message from the United States and the international community that Iran needs to meet its obligations as defined by the Security Council and its continued refusal to do so will only cause pressure to increase."