Choe Thae Bok, right, chairman of North Korea's Supreme People's Assembly, talks to an unidentified official after arriving at the airport in Beijing, China, on Tuesday. (Alexander F. Yuan/Associated Press)

China is growing frustrated with North Korea and some Chinese officials would be open to the idea of a unified Korea run by the south, according to leaked U.S. diplomatic cables released by the WikiLeaks website.

The release comes as China welcomes an envoy from North Korea after last week's shelling of a South Korean island, which killed four people. Choe Thae Bok, the chairman of North Korea's Supreme People's Assembly, arrived in Beijing on Tuesday for a visit following a call last week from China for emergency consultations.

In one of the leaked documents, South Korea's then vice-foreign minister, Chun Yung-woo, is quoted as telling U.S. ambassador Kathleen Stephens that China "would be comfortable with a reunified Korea controlled by Seoul and anchored to the U.S. in a 'benign alliance' as long as Korea was not hostile towards China."

Chun said Chinese diplomats also told him that trade and labour export opportunities in a reunified Korea could further induce Chinese acquiescence.

However, the diplomatic cables also indicate that China, which fought on North Korea's side in the 1950-53 Korean War, would not accept the presence of U.S. troops north of the demilitarized zone that currently forms the North-South border.

In another leaked U.S. document, China's vice-foreign minister He Yafei is quoted as saying North Korea was acting like a "spoiled child" trying to get the attention of the adult — the United States — by carrying out missile tests in April 2009.

Other cables outline China's ideas of what should happen if the North collapsed after leader Kim Jong-il's death, saying Chinese officials believe the country could absorb about 300,000 North Koreans without outside help, The Guardian reported.

"What's awkward for the Chinese is that the cables indicate division on North Korea," CBC's China correspondent Anthony Germain reported. "And equally important: some of China's own diplomats question whether Beijing has any real influence on Pyongyang, at a time when China is trying to play a role during the current crisis. "

Germain noted that it's important to keep in mind that the information contained in the cables are statements of opinion, not policy.

Chinese Foreign Ministry spokesman Hong Lei said China had noted the leaked cables but would not comment on specific content.

"China always supports the North and South sides of the Korean peninsula to have dialogue and consultation to improve their relations," Hong said at a regularly scheduled news conference.

U.S. Secretary of State Hillary Clinton said her government "deeply regrets" the disclosure of information intended to be confidential. Meanwhile, U.S. Attorney General Eric Holder said his department is conducting a criminal investigation into the leak of the diplomatic cables to WikiLeaks.

WikiLeaks made more than 250,000 diplomatic documents available to five newspapers, including the New York Times.

The whistleblower website published 220 cables on its own website on Sunday. More cables were expected to be released throughout the week.

With files from The Associated Press