Iran’s new President Hassan Rouhani has said that his country would never build nuclear weapons.
Mr Rouhani also told US broadcaster NBC he had full authority to negotiate with the West over Tehran’s controversial uranium enrichment programme.
And he described a recent letter sent to him by US President Barack Obama as “positive and constructive”.
Earlier, Iran reportedly freed 11 political prisoners including noted human rights lawyer Nasrin Sotoudeh.
The eight women and three men are said to also include the reformist politician Mohsen Aminzadeh.
In his election campaign earlier this year, Mr Rouhani promised to free political prisoners. He also pledged a more moderate and open approach in international affairs.
He is due to visit New York next week for a meeting of the UN General Assembly.
‘Subtle and tiny steps’
The BBC’s Iran correspondent James Reynolds says Mr Rouhani’s decision to speak to a major US news organisation shows the importance to his government of reconciliation with Washington.
Iran is under UN and Western sanctions over its controversial nuclear programme. It says it is enriching uranium for peaceful purposes but the US and its allies suspect Iran’s leaders of trying to built a nuclear weapon.
In an extract released ahead of the interview’s full broadcast, the Iranian president says: “It could be subtle and tiny steps for a very important future.”
The White House said on Wednesday that there had been an exchange of letters between President Obama and President Rouhani.
“In his letter the president indicated that the US is ready to resolve the nuclear issue in a way that allows Iran to demonstrate that its nuclear program is for exclusively peaceful purposes,” said White House spokesman Jay Carney.
“The letter also conveyed the need to act with a sense of urgency to address this issue because, as we have long said, the window of opportunity for resolving this diplomatically is open, but it will not remain open indefinitely,” he added.
The moves come a day after Iran’s Supreme Leader, Ayatollah Ali Khamenei, gave the strongest sign yet of Iran’s potential flexibility in future talks with the West.
In a meeting with Revolutionary Guards he said: “I don’t oppose diplomacy. I am in favour of showing a champion’s leniency. A wrestler may give way for tactical reasons, but should remember who is its opponent and enemy.”
The head of Iran’s nuclear agency told reporters in Tehran on Wednesday that he expected “a breakthrough” this year in settling the nuclear issue with the West.
“We are very optimistic about the process that has started to resolve the nuclear issue,” said Ali Akbar Salehi.
Earlier on Wednesday, Nasrin Sotoudeh’s husband, Reza Khandan, said she had been dropped off at their home by prison officials on Wednesday evening.
He said she had been unaware that she was about to be released.
“I am happy that she joined us, particularly as our younger child is starting school for the first time,” he told AP news agency.
“We are very happy but we will be happier if other prisoners are freed.”
She was arrested in 2010 and jailed for six years on charges of acting against national security.
Ms Sotoudeh – winner of the European Parliament’s 2012 Sakharov Prize for Freedom of Thought – is a well-respected and outspoken human rights lawyer known for taking on high-profile political cases.
During her captivity in Tehran’s Evin jail, she went on hunger strike to protest against her prison conditions as well as restrictions imposed on her family.
Mohsen Aminzadeh, a former deputy foreign minister under President Mohammed Khatami, was jailed in 2010 for organising protests and spreading propaganda against the system.
He was a prominent supporter of the defeated presidential candidate Mir Hossein Mousavi.
Analysts say that since President Rouhani’s election, there have been growing calls for the release of political prisoners.
According to an investigation by the UK’s Guardian newspaper, there are close to 800 political prisoners and prisoners of conscience in Iran.
They include journalists, lawyers, human rights activists, bloggers, feminists, Christian priests, Sunni clerics, the entire leadership of the Bahai faith in Iran, and others.