Soon after President Barack Obama took office in 2009 promising to reach out to US enemies, North Korea tested a missile and then a nuclear bomb and stormed out of US-backed talks.

On Wednesday, barely two months after veteran leader Kim Jong-Il died, North Korea agreed to shut down its nuclear program including uranium enrichment and to allow back UN inspectors, with the United States offering food assistance.

The deal came despite initial doubts in Washington that North Korea would take any decisive action so soon amid expectations that Kim's son and successor Kim Jong-Un, who is in his late 20s, would need to prove his toughness.

While few are ready to proclaim the little-known Kim Jong-Un to be a peacemaker, US officials and experts are guardedly upbeat that North Korea's transition has progressed more smoothly than expected and, possibly, that the young leader is responsive to overtures from the outside.

Bruce Klingner, a senior research fellow at the conservative Heritage Foundation, said that while a long road lay ahead, the deal was a "positive first step" and marked a "major reversal" by North Korea after years of refusing to freeze its nuclear program.

"This is particularly surprising coming only two months after Kim Jong-Il's death," Klingner said. "One might have expected the regime to pursue a longer mourning period."

Bruce Cumings, the chair of the history department at the University of Chicago and author of several books on Korea, said that North Korea may have calculated that Obama will win reelection in November and regretted that it had carried out missile and nuclear tests at the start of his first term.

"At the time I thought this was stupid of them, because Obama had pledged to talk with enemy regimes that would 'unclench their fists,'" Cumings said.

"Certainly this new agreement is a distinct unclenching, and implicitly acknowledges that their behavior in early 2009 got them nothing," he said.

Cumings noted that Kim Jong-Un -- unlike his father or grandfather Kim Il-Sung, the founder of North Korea -- has been exposed to the West through an education in Switzerland.

But Cumings cautioned that North Korea had a collective leadership and that Kim Jong-Un's personal role would only come into play on "the most critical decisions of war and peace."

"All things considered, though, this is a positive development and suggests that the new leadership is turning toward reform, and much less belligerence than in the past few years," Cumings said.

A senior American official said that despite the change in top leader in Pyongyang, US envoys who held talks with North Korea last week in Beijing still sat across from Kim Kye-Gwan, Pyongyang's veteran nuclear negotiator.

"What we are seeing is a sign of continuity. I think overall the early stages of the transition have been relatively uneventful," the official said on condition of anonymity.

Critics of the Obama administration say that North Korea has been eager for talks not because of any change of heart on nuclear weapons but because the regime wants food aid ahead of mass celebrations for Kim Il-Sung's 100th birth anniversary on April 15.

The official said that the United States would strictly monitor delivery and only provide goods suited to children and pregnant women -- not items that can be easily diverted to the army.

Admiral Robert Willard, the head of the US Pacific Command, which covers Asia, testified before a Senate committee on Tuesday that North Korea's succession "appears to be on course" and that Kim Jong-Un was likely to follow his father's core strategy -- including pursuit of nuclear weapons.

Gordon Flake, executive director of the Mansfield Foundation, said that North Korea closed down for a much longer period after Kim Il-Sung's death and the regime -- not the United States -- initiated the latest talks in Beijing.

"That's a pretty clear indication that they're eager and willing to engage and negotiate," Flake said.

"You can debate what their long-term objectives are, but there is no question that things are running relatively smoothly in North Korea right now."

Key developments in N. Korea nuclear standoff
Seoul (AFP) March 1, 2012 - North Korea has announced it will suspend nuclear and missile tests and its uranium enrichment programme as part of a deal that includes US food aid.

Here are key dates since the latest nuclear standoff erupted:

2002

- October: The US says North Korea is running a secret highly enriched uranium programme in violation of a 1994 denuclearisation accord -- a charge it denies. Oil shipments under the 1994 pact are suspended.

- December: The North unseals its plutonium-producing Yongbyon reactor for the first time since 1994 and expels inspectors from the International Atomic Energy Agency (IAEA).

2003

- January 10: North Korea says it will quit the nuclear Non-Proliferation Treaty.

- August 27-29: First round of six-party disarmament talks -- involving the two Koreas, China, Japan, Russia and the United States -- is held in Beijing.

2005

- February 10: North Korea declares it has manufactured nuclear weapons for self-defence.

- September 19: At six-party talks, North Korea agrees to scrap its nuclear programme and return to the Non-Proliferation Treaty in return for security and diplomatic guarantees and energy aid.

- November 9-11: New round of talks collapses, with the North insisting that US-led financial sanctions which froze its accounts in a Macau bank be lifted.

2006

- October 9: North Korea tests a nuclear weapon.

- October 31: Following secret talks with his North Korean counterpart, US negotiator Christopher Hill announces the North has agreed to return to the six-party talks.

2007

- February 13: China announces deal under which North Korea will disable nuclear plants at Yongbyon and allow IAEA inspectors to return. In exchange it will get one million tonnes of fuel aid and be removed from a US list of terrorist states.

- July 14: First shipment of fuel aid reaches North Korea, along with IAEA inspectors. US says Yongbyon has been shut down.

- October 3: Six nations announce deal under which the North will declare all nuclear programmes and disable Yongbyon by the end of 2007. Disablement starts in November.

2008

- June 26: North Korea hands over declaration on its nuclear programme.

- August 26: North Korea says it has stopped disablement and will consider restoring the plants in protest at US failure to drop it from the terrorism blacklist.

- October 11: US says it is removing North Korea from its list of state sponsors of terrorism.

- December 8-11: Six-party talks end in stalemate after failing to agree on how to verify the North's declaration.

2009

- April 5: North Korea launches long-range rocket which it says put a communications satellite into orbit. The United States says the launch was actually a missile test.

- April 13: UN Security Council unanimously condemns North Korea for the launch and tighten existing sanctions.

- April 14: North Korea announces it will quit the six-nation talks, reopen disabled plants and strengthen its nuclear deterrent.

- May 25: North carries out a second nuclear test.

-June 12: UN Security Council passes resolution enforcing new sanctions.

2010

- November 12: North unveils uranium enrichment plant to visiting US scientists. Experts say it could be reconfigured to make atomic weapons.

2011

- July 22: North and South Korean nuclear envoys meet in Bali to discuss possible resumption of six-party talks.

- July 28-29: US and North Korea hold similar talks in New York, meet again in Geneva in October.

- December 17: North Korean leader Kim Jong-Il dies and is succeeded by his youngest son Kim Jong-Un.

2012

- February 23-24: US and North Korea hold third round of bilateral talks.

- February 29: North says it will suspend nuclear and missile tests and its uranium enrichment programme.