Iranian President Hassan Rouhani said in a television interview Wednesday  that his government would never develop nuclear weapons and that he had full authority to negotiate a nuclear deal with the West, NBC News reported.
Coming amid increasing signs of a possible thaw in ties with the U.S., Rouhani also said the tone of the letter he received recently from U.S. President Barack Obama , in an exchange of messages between the two leaders, was “positive and constructive.”
“It could be subtle and tiny steps for a very important future,” Rouhani said, in another sign that he may be seeking a thaw in relations between Iran and the West after years locked in a standoff over Tehran’s nuclear program.
The newly elected leader’s first broadcast interview with an American network also comes ahead of his first visit to the U.S. next week where he will address the U.N. General Assembly.
There is heightened speculation that Obama and Rouhani could have some kind of informal meeting on the sidelines of the General Assembly.
The White House said for the second day running Tuesday that it had no current plans for such an encounter – but did not dismiss the possibility.
U.S. President Barack Obama pledged Tuesday to test the sincerity of signs that Rouhani may be ready for a newly productive nuclear dialogue.
But days after revealing that he and Rouhani had swapped letters, Obama said Iran would have to demonstrate its own seriousness by agreeing not to “weaponize nuclear power.”“There is an opportunity here for diplomacy,” Obama told the Spanish language TV network Telemundo. “I hope the Iranians take advantage of it. There are indications that Rouhani, the new president, is somebody who is looking to open dialogue with the West and with the U.S. – in a way that we haven’t seen in the past.”
“And so we should test it,” Obama said.
Hopes for a new round of nuclear talks between Iran and world powers expected to resume soon were boosted earlier Tuesday by cryptic remarks by Iran’s Supreme Leader Ayatollah Ali Khamenei. 
Khamenei, who bears ultimate responsibility for the nuclear issue, said that sometimes flexibility was necessary in diplomacy.
On Sept. 11, Rouhani said he had the tacit support of Khamenei for “flexibility” in nuclear talks. Rouhani has previously said he wants to allay Western concerns, but he will not renounce Iran’s goal of an independent civil nuclear program.
NBC’s Ann Curry told the broadcaster following the interview with Rouhani that his remarks were “categorical” that Iran would never pursue nuclear weapons.
In excerpts of Curry’s interview posted on the NBC website , ahead of the full broadcast interview to be aired later Wednesday night in the U.S., Rouhani said of the recent exchange of letters that “I believe the leadership in all countries could think in their interests and not under the influence of pressure groups. I hope to witness such an atmosphere in the future.”
In another development interpreted as a sign that Iran’s hard-line policies may be easing under the new president, Iran released human rights lawyer Nasrin Sotoudeh,  seen by campaign groups as Iran’s highest profile political prisoner.
Other prisoners linked to the protests after the disputed 2009 re-election of President Mahmoud Ahmadinejad were also freed, opposition website Kaleme reported.