WASHINGTON — Iranian President Hasan Rouhani said Wednesday that his country has never sought and will never seek a nuclear bomb, telling NBC News in an interview that he has full authority to resolve a standoff with the West.

Rouhani spoke to the American television network in Tehran just days before he is to make his first appearance as president on the world stage when he attends the United Nations General Assembly in New York. US officials will be watching next week’s visit closely for signs that Rouhani will warm relations with the West and take a more moderate line in the next negotiations on Iran’s disputed nuclear program.

“We have never pursued or sought a nuclear bomb and we are not going to do so,” Rouhani said, according to an NBC translation of the interview. “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.”

It was a claim Iran has made before, that its nuclear activities are purely peaceful. However, the US and its allies suspect Iran is trying to develop a nuclear weapon, a feat some experts say the country might be able to accomplish as early as next year.

Rouhani also addressed a question that many in the US have been asking: Does he really have the power to make major decisions and concessions on the nuclear issue?

Iranian Supreme Leader Ayatollah Ali Khamenei is known to control all important matters of state, including nuclear.

“In its nuclear program, this government enters with full power and has complete authority,” Rouhani said. “We have sufficient political latitude to solve this problem.”

Rouhani is considered a relative moderate in Iran’s hard-line clerical regime. He campaigned on a promise to seek relief from punishing U.S. and Western sanctions that have slashed Iran’s vital oil exports by more than half in the past two years, sent inflation soaring and severely undercut the value of its currency.

Turning to the Syria, Rouhani addressed US allegations that the Iranian-allied regime was behind a chemical weapons attack near Damascus last month. He said his country seeks peace and stability and the elimination of weapons of mass destruction in the entire region.

Asked whether President Barack Obama had looked weak by backing off a military strike on the Syrian regime, Rouhani responded: “We consider war a weakness. Any government that decides on war, we consider a weakness. And any government that decides on peace, we look on it with respect for peace.”

Rouhani also said he received a “positive and constructive” letter from Obama congratulating him on his election in June. In it, he said Obama raised some issues the US president was concerned about and that he had responded to the points Obama raised.

“From my point of view, the tone of the letter was positive and constructive,” Rouhani said. “It could be subtle and tiny steps for a very important future.”

White House spokesman Jay Carney said Wednesday there were no current plans for Obama to meet Rouhani at the UN General Assembly.

“I think it’s fair to say that the president believes there is an opportunity for diplomacy when it comes to the issues that have presented challenges to the United States and our allies with regards to Iran,” he said. “And we hope that the Iranian government takes advantage of this opportunity.”

Carney said the US will test Rouhani’s assertions that he wants to improve relations with the international community.

He also noted that Obama had confirmed the exchange of letters with Rouhani. In his letter, Obama indicated that the US was ready to resolve the nuclear issue in a way that would allow Iran to demonstrate that its program was exclusively for peaceful purposes, Carney said.

“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,” Carney said.

Rouhani’s latest comments are part of a series of developments indicating a rapprochement between Iran and the US whose mutual relations remained hostile under the eight-year leadership of former president Mahmoud Ahmadinejad.

The United States and Iran cut off formal ties after students and Islamic militants stormed the US Embassy in Tehran and took American diplomats hostage in 1980.

Officials from both countries have expressed readiness to find a diplomatic solution to the decade-long dispute over Iran’s nuclear program, over which the West has imposed economic sanctions on the Islamic Republic.

On Tuesday, Ayatollah Khamenei said Iran was not opposed to dialogue with the West concerning its nuclear program, did not seek the bomb, and would show flexibility in negotiations.

“I am not opposed to correct diplomacy,” Khamenei said. “I believe in what was named many years ago as ‘heroic flexibility.’”

Khamenei’s comments came a day after German news magazine Der Spiegel reported that Rouhani was prepared to shut down Iran’s uranium enrichment facility at Fordo in exchange for eased Western sanctions. The report was later denied by Iran’s nuclear chief Ali Akbar Salehi.

“A wrestler sometimes shows flexibility for technical reasons. But he does not forget about his opponent nor about his main objective,” Khamenei added.

“We do not believe in nuclear weapons because of our beliefs, not for the sake of the US or other countries, and when we say that no country should possess nuclear weapons, we ourselves are definitely not trying to possess them,” he said.

In an apparent reply to Khamenei’s statements, Obama said Tuesday that he would test Iran’s willingness to engage in dialogue about its unsanctioned nuclear program.

“There is an opportunity here for diplomacy,” Obama said. “And I hope the Iranians take advantage of it.”

“There are indication that Rouhani, 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. And so we should test it,” Obama told Spanish-language network Telemundo.

The two leaders will both attend next week’s United Nations General Assembly in New York, with Obama expected to address the plenum on Tuesday morning, and Rouhani speaking on Tuesday afternoon. Officials says no meeting has been scheduled between them, although Carney said Tuesday that he doubted Obama would “duck into another hall” to avoid the Iranian president should they encounter each other in the halls of the UN.