Iran's new President Hassan Rouhani says the world should grab the new opportunity for constructive interaction with Iran.
In his first news conference since Friday's election, Mr Rouhani described as "unfair" sanctions imposed on his country. He also said Tehran would not suspend uranium enrichment activities.
The West suspects Iran of trying to build nuclear weapons. Iran says its programme is entirely peaceful.
"Our nuclear programmes are completely transparent," Mr Rouhani told a packed hall in the capital Tehran.
"But we are ready to show greater transparency and make clear for the whole world that the steps of the Islamic Republic of Iran are completely within international frameworks," he said.
Mr Rouhani also said relations between Iran and the United States were an old wound that needed to be healed.
A BBC correspondent said Mr Rouhani's win has been greeted enthusiastically by people in Iran who are opposed to the ultraconservative regligious leadership and hope for change.
He has said, himself, that the opportunity for improved relations with other nations has been created by the Iranian people, because of they way they voted - particularly the young people who chose moderation over extremism.
Mr Rouhani won just more than 50% of the vote in the election on Friday, avoiding a run-off vote.
The president has limited powers, with key policy decisions being taken by the Supreme Leader, Ayatollah Ali Khamenei.
Mr Rouhani was formerly Iran's top nuclear negotiator.