U.S. and North Korean diplomats began talks Monday on Pyongyang's nuclear program, the second direct encounter between the two sides in less than three months.

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Ri Kun, North Korean envoy for the United States, leaves his hotel for the U.S. mission in Geneva for talks with American representatives. (Denis Balibouse/Reuters)

Mobbed by reporters as they left their lakeside hotel for a first meeting at the United States' UN mission in Geneva, American diplomats declined to reveal their goals for the two-day talks.

Stephen Bosworth, the U.S. top envoy on Pyongyang, said the two sides hadn't met Sunday despite staying — by design or coincidence — in the same hotel. He was accompanied by Glyn Davies, the U.S. ambassador to the International Atomic Energy Agency, who is taking over the negotiating brief in future talks.

Their opposite on the North Korea's delegation is First Vice Foreign Minister Kim Kye Gwan.

U.S. diplomats have previously said they want North Korea to adhere to a 2005 agreement it reneged on requiring verifiable denuclearization in exchange for better relations with its Asian neighbours.

The talks could also touch upon long-standing issues such as food aid to the chronically impoverished North, reuniting separated families on the Korean peninsula and recovering the remains of troops missing in action.

North Korea's closest ally China urged Pyongyang to improve its strained ties with longtime foes the United States and South Korea, China's official Xinhua News Agency reported Monday.

Beijing wants to revive the stalled six-nation disarmament negotiations, which also include South Korea, Japan and Russia. North Korea walked out on the talks in 2009 — and exploded a second nuclear-test device — but now wants to re-engage.

Panetta criticizes North Korea's 'reckless' behaviour

As talks in Geneva were getting underway, U.S. Defence Secretary Leon Panetta lashed out at North Korea for "reckless and provocative" acts and criticized China for a secretive expansion of its military power.

Panetta, who arrived at the U.S. air base in Yokota, Japan, was commenting on the second leg of a weeklong Asia tour in an opinion piece published Monday by Japan's Yomiyuri newspaper before his arrival.

He wrote that Washington and Tokyo share common challenges in the Asia-Pacific. "These include North Korea, which continues to engage in reckless and provocative behaviour and is developing nuclear weapons and ballistic missiles, which pose a threat not just to Japan but to the entire region," he wrote.

At a question-and-answer session with U.S. and Japanese troops at Yokota, Panetta said that despite coming budget cuts there will be no reduction in U.S. forces in Asia and the Pacific.

On the contrary, he said, the Obama administration intends to "strengthen our position" in the region.