Iran will never seek nuclear weapons, newly elected President Hassan Rowhani vowed Wednesday, as he reached out to longtime enemy the United States.

In a US television interview days before he travels to New York for the UN General Assembly, Rowhani praised US President Barack Obama for taking a "positive" approach toward Tehran in a letter.

"Under no circumstances would we seek any weapons of mass destruction, including nuclear weapons, nor will we ever," Rowhani told NBC News.

"We have never pursued or sought a nuclear bomb, and we are not going to do so," he said, according to the US network.

Rowhani repeated Iran's position that the clerical state -- suffering from US-led sanctions following sensitive uranium work -- was solely "looking for peaceful nuclear technology."

Rowhani, considered more moderate than his rivals, swept to power in June on promises to help repair Iran's economy and to ease tensions with the West.

His stance has been met alternately with cautious optimism and skepticism in Washington, where experts note that supreme leader Ayatollah Ali Khamenei ultimately controls foreign policy.

Rowhani told NBC News: "In its nuclear program, this government enters with full power and has complete authority."

"The problem won't be from our side," he was quoted as saying. "We have sufficient political latitude to solve this problem."

Asked about Rowhani's interview, US Defense Secretary Chuck Hagel said he was "glad" to hear his remarks and that Obama had always been "willing to talk."

"But I think the next step here is let's see how Iran's actions match their words," Hagel told the "PBS Newshour" on public television.

Obama recently acknowledged that he exchanged letters with Rowhani. The United States and Iran have had no diplomatic relations since the aftermath of the 1979 Islamic revolution that overthrew the Western-oriented shah.

In an interview Tuesday, Obama pledged to test the "opportunity here for diplomacy."

"I hope the Iranians take advantage of it. There are indications that Rowhani, the new president, is somebody who is looking to open dialogue with the West and with the United States -- in a way that we haven't seen in the past," Obama told Spanish-language network Telemundo.

The White House has played down chances of Obama meeting Rowhani at the UN General Assembly, while not completely ruling it out.

At the very least, Rowhani is virtually certain to project a different image at the UN than his predecessor Mahmoud Ahmadinejad, who was known for his harsh denunciations of Israel and questioning of the Holocaust.

Ahead of the UN visit, Iran on Wednesday freed prominent human rights lawyer Nasrin Sotoudeh and several other political prisoners, winning cautious praise from the West.

Rowhani, in the interview to NBC News, said that Obama's letter was "positive and constructive."

"I believe the leaders in all countries could think in their national interest and they should not be under the influence of pressure groups," he said, in a possible allusion to the pro-Israel lobby in the United States.

Israeli Prime Minister Benjamin Netanyahu has described Rowhani as a "wolf in sheep's clothing" and threatened military action to prevent an Iranian nuclear bomb.

Despite the flirtation between Iran and the United States, the two countries are at loggerheads over Syria's bloody civil war.

Rowhani was cautious when asked whether Obama looked weak by shelving a threatened strike on Syria over President Bashar al-Assad's alleged use of chemical weapons.

"Any government or administration that decides to wage a war, we consider a weakness. And any government that decides on peace, we look on it with respect to peace," Rowhani told NBC News.

Iran's Shiite regime counts Assad -- a secular leader from the heterodox Alawite sect -- as its closest regional ally. The rebels enjoy support from Sunni Arab monarchies Saudi Arabia and Qatar.

Obama put off a strike on Syria after Russia and the United States reached a plan under which Assad agreed to hand over chemical weapons.