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 over Tehran's controversial uranium enrichment programme with the West.
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.