China Thursday welcomed North Korea's agreement to freeze nuclear activities in return for massive US food aid, a deal that raised cautious hopes of eased tensions under Pyongyang's new young leader.

South Korea and Japan also hailed Pyongyang's commitment to suspend its uranium enrichment programme along with nuclear and long-range missile tests, and to let UN nuclear inspectors monitor the deal.

The announcement follows the death in December of longtime leader Kim Jong-Il and the transition to his untested son Jong-Un.

The deal could boost the son's prestige in the run-up to a major celebration next month, marking 100 years since the birth of the Kim dynasty's late founding leader Kim Il-Sung.

The breakthrough followed US-North Korean talks in Beijing last week, the first under the new regime.

China, the North's sole major ally and economic prop, welcomed the warmer relations between North Korea and its longtime foe the United States.

"China is willing to work with relevant parties to continue to push forward the six-party talks process, and play a constructive role to realise long-term peace and stability on the Korean peninsula and northeast Asia," said foreign ministry spokesman Hong Lei.

The six-nation nuclear disarmament talks have been stalled for some three years. But the two Koreas, Japan, China, Russia and the United States have been talking for months about ways to revive them.

The disclosure in November 2010 of the enrichment programme, which could give the North a second path to an atomic bomb, lent urgency to the diplomacy.

Amid the latest progress, the United States said North Korea's top nuclear negotiator Ri Yong-Ho would pay a rare visit next week for talks at a US university.

The State Department said the meetings at Syracuse University in upstate New York -- which will involve scholars but not current US officials -- were part of a so-called "track-two dialogue".

South Korea, whose relations with its neighbour have remained icy under the new leadership, has backed the latest agreement disclosed simultaneously by the US and North Korea on Wednesday night.

Russia's foreign ministry welcomed the moratorium on nuclear testing and uranium enrichment.

Japan's Foreign Minister Koichiro Gemba said the deal was "an important step" but called for concrete action. Tokyo still wants "the complete and verifiable denuclearisation of the Korean peninsula", he said.

That is also the stated goal of the six-party talks which have dragged on since August 2003. The North angrily quit the forum in April 2009 and staged its second atomic weapons test a month later.

Analysts said Wednesday's deal could help revive the talks, but many remain sceptical that the North will ever abandon its nuclear weaponry.

"At this point the best that can be done is to freeze the nuclear programme," said Peter Beck, Korea representative for the Asia Foundation.

"For now, the agreement is a welcome development. Talking is better than not talking and a freeze is better than an unfettered nuclear programme."

Kim Jong-Un, Beck told AFP, appeared to have decided that "feeding his people is seen as more important than expanding nuclear facilities".

The United States has pledged 240,000 tonnes of food designed for young children and pregnant women and difficult to divert to the North's military.

The North has suffered persistent severe food shortages since a 1990s famine, but still spent massively on a nuclear programme thought to have produced enough plutonium for six to eight weapons.

It says it needs such a deterrent against US hostility.

Washington "reaffirms that it does not have hostile intent" towards the North and is prepared to improve the relationship, said State Department spokeswoman Victoria Nuland.

Pyongyang said it would let the International Atomic Energy Agency monitor the suspension of uranium enrichment. Agency chief Yukiya Amano called this "an important step forward" and said his inspectors were ready to return.

US administration officials, already under fire in an election year from Republican critics, were cautious about prospects.

"Today's announcement represents a modest first step in the right direction," said Secretary of State Hillary Clinton. "We of course will be watching closely and judging North Korea's new leaders by their actions."

EU foreign policy chief Catherine Ashton also gave a cautious welcome to Pyongyang's announcement, while France said it was an "encouraging advance" but urged North Korea to return to talks.

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.