Iranian President Hassan Rouhani vowed Wednesday that his country will never develop nuclear weapons, telling NBC News that he is open to diplomatically resolving issues surrounding his country's controversial nuclear program. "We have never pursued or sought a nuclear bomb and we are not going to do so," Rouhani said. Later, he added, "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." In an interview with NBC's Ann Curry, Rouhani said that -- even with Supreme Leader Ayatollah Ali Khamenei, a looming presence in Iranian society -- he has "full power and has complete authority" to make a deal with others on nuclear matters. "The problem won't be from our side," the Iranian president said. "We have sufficient political latitude to solve this problem." Opposition to Iran's atomic program, coupled with what critics see as Tehran's intransigence in failing to cooperate with international officials, had led to harsh sanctions and stirred concerns that the dispute could devolve into a military conflict. Yet Rouhani appeared relatively optimistic Wednesday. He spoke about getting a letter from U.S. President Barack Obama after his recent election and inauguration, saying the U.S. president congratulated him and raised certain issues. Rouhani said he wrote back offering Iran's viewpoint, describing the tone of the exchange as "positive and constructive." "It could be subtle and tiny steps for a very important future," the Iranian president told NBC, according to video on the network's website. "I believe the leaders in all countries could think in their national interests and that they should not be under the influence of (interest) groups." Report: Iran takes key step in nuclear reactor construction. Even as it has resisted attempts to international regulators to assess its development, Iran has long insisted its nuclear program's aim is to produce power, not weapons. Last month, Rouhani said the United States and other nations "need to recognize that our activities are totally peaceful and legal." If they do and there are "negotiations without threats," Rouhani added, then "the way for interaction is open." The 64-year-old cleric, who is considered moderate, won the June elections with reformist backing after a campaign in which he stressed "hope and prudence." A former nuclear negotiator himself, he vowed to reduce the high tension between Iran and the outside world. Rouhani has military experience as well, having once commanded Iranian air defenses and led three war and defense councils. He was national security adviser for 13 years before his presidential predecessor, Mahmoud Ahmadinejad, took office in 2005. Iranian human rights activist freed. CNN's Greg Botelho contributed to this report.

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Iranian President Hassan Rouhani talks to NBC News about his nation's nuclear program. Rouhani says his government "has complete authority" to reach a deal with the U.S., others. He calls a recent exchange of letters with U.S. President Obama as "positive and constructive" Considered a moderate, Rouhani was elected president earlier this year.

The nation's capital was blanketed by downed trees and power lines Saturday after a killer storm with furious winds whipped through. Bruised and battered, the District of Columbia was reeling from damage as skies cleared and the temperature began to soar again. A man died in the city, electrocuted by a downed power line, police said. His wife was in critical condition. In neighboring Virginia and Maryland, seven people were killed by fallen trees, authorities said. Virginia Gov. Bob McDonnell declared a state of emergency Saturday morning. Traffic flowed through major arteries, but smaller roads were a different story. Trees were down in every ward, said D.C. City Administrator Allen Lew. In 19 intersections, the traffic lights were knocked out. Saturday afternoon, more than 67,000 Washington residents still had no power. Another 1 million were in the dark in Virginia. In hard-hit Fairfax County, nearly half of all residents had no electricity. That meant no fans. No air-conditioning. No refrigerators. Authorities encouraged people without power to head to public recreation facilities or libraries to stay cool. But some of Washington's libraries were without power, too, Lew said. McDonnell said 911 emergency systems experienced problems statewide, with entire grids down in Fairfax County and Prince William County. Officials are urging residents to contact their local police and fire departments if in need of help. Much of the problem was due to the trees -- some old and huge -- that snapped in winds gusting at 80 miles per hour. Pepco requested 1,000 crews from around the nation, but it could take them a few days to arrive, said Joseph Rigby, president of the energy company. So far, he said, he has secured 200 crews. But even with the manpower, Rigby urged patience. More erratic weather could hamper recovery speed. There was a possibility of a new line of thunderstorms Saturday night, the National Weather Service said. And then, there was the heat. The Washington area hit 104 degrees on Friday, topping a record of 101 reported in 1934, the weather service said. And it was blistering again Saturday with the heat index topping 100 degrees. The power outages were so great in Fairfax County that officials gave up on the idea of cooling centers. Go to malls, they told people, or other public places that were air-conditioned. In Maryland, the state's emergency management agency reported the opening of cooling centers in Montgomery and Hartford counties. Pepco's Rigby said some areas in and around the capital could be without power for a week. That meant a lot of people will again have trouble sleeping at night. 3 states declare emergencies as heat, deadly storms bring misery to millions.

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8 people are killed in the Washington area. More than a million people are without power. That meant no fans or AC as the heat index was again above 100 degrees.