Iran's new President Hassan Rouhani has said that his country will 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 freed noted human rights lawyer Nasrin Sotoudeh and reportedly released 10 other political prisoners.
The 10 other detainees - seven women and three men - are said to include 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.
The BBC's Iran correspondent James Reynolds says Mr Rouhani's interview 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 a wide-ranging interview with NBC News in Tehran, Mr Rouhani said Iran had "never pursued or sought a nuclear bomb and we are not going to do so".
"We have time and again said that under no circumstances would we seek any weapons of mass destruction, including nuclear weapons, nor will we ever."
He added: "In its nuclear programme, this government enters with full power and has complete authority. We have sufficient political latitude to solve this problem."
President Rouhani said his government wanted the Iranian people to be "completely free" in their private lives.
He said a "commission for citizens' rights" was to be set up in the near future.
"In today's world, having access to information and the right of free dialogue and the right to think freely is the right of all people, including the people of Iran,'' he said, according to NBC's translation of the interview.
Mr Rouhani said he had received a letter from President Obama congratulating him on his election in June.
He said Mr Obama had raised some issues and that he had responded to the points raised.
"From my point of view the tone of the letter was positive and constructive," Mr Rouhani said.
"It could be subtle and tiny steps for a very important future."
'Sense of urgency'
The White House on Wednesday gave details of the recent 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 programme 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.
Nasrin Sotoudeh spoke to the BBC's World Service a few hours after her release from prison.
"It was only outside the prison walls that they told me I was free. At that moment I was very happy," Ms Sotoudeh said.
Ms Sotoudeh was arrested in 2010 and jailed for six years on charges of acting against national security. She said that as a political prisoner she was not allowed phone or internet communication with the outside world, and she was worried her family could face punishment.
She described being reunited with her family: "My children could see me from the intercom. They were very happy to see me, and me them."
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.
She told the BBC she planned to "continue with my activities as before, in order to establish a proper judicial system in my country."
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.