BEIJING, June 2 (Reuters) - The top item on the Chinese website of Beijing's embassy in Pyongyang is a condemnation of North Korea's nuclear test.

That, and a recent blast of blunt criticism of North Korea in China's state-run press, suggest the rancour that officials feel towards their communist neighbour -- anger likely to bring Beijing behind a U.N. resolution condemning the May 25 test and threatening fresh sanctions.

North Korea's second nuclear test took place 85 km (53 miles) from China's border, and the tremors from the blast forced many schools on the Chinese side to evacuate, wrote Zhang Lianggui, a prominent Chinese expert on the North.

He warned of catastrophe if Pyongyang mishandles a nuclear test.

"Future generations of the Korean people will have no place of their own, and China's reviving northeast will burst like a bubble," Zhang wrote in the Global Times, a popular tabloid, on Tuesday.

"This is an unprecedented threat that China has never faced in its thousands of years."

On Monday, a commentary in the same paper called North Korea a "strategic burden" for China. Not the kind of language the government would have allowed earlier this year, when the focus was on celebrating 60 years of ties with the Communist North.

Zhan Debin, an expert on Korea at Fudan University in Shanghai, wrote in the paper that the Chinese government could soon be pushed to abandon its usual reticence.

"If this continues, China will not be able to stall international expectations by saying that North Korea doesn't listen or that we have no influence," wrote Zhan.

If Pyongyang continues raising the international stakes, Zhan added, war cannot be ruled out, and North Korea will "either continue trapped in a Cold War or will swiftly disappear".

Such harsh words may not have the express approval of China's leaders. But they reflect the government's growing impatience with its neighbour.

STRATEGIC BUFFER

China has long regarded the North as a strategic buffer against the extension of U.S. and allied forces up to its 1,416-km (880-mile) frontier with the North.

But Beijing also fears North Korea's nuclear threats could tip the region into destabilising and expensive military rivalry.

For all the harsh words in the Chinese media, however, the government may not be so forceful when the U.N. Security Council considers fresh sanctions against the North.

Apart from the May 25 condemnation of the test, Chinese Foreign Ministry officials have avoided strong commentary about North Korea, which depends on its 1950-53 Korean War ally China for much of its food and oil.

In 2006, China backed a U.N. resolution condemning the North's first nuclear test. But it fended off demands for sanctions that could choke its economic lifeline to Pyongyang.

"China will be extremely cautious about new sanctions this time," Liu Jiangyong, an expert on East Asian security at Tsinghua University in Beijing, told Reuters.

"China won't agree to excessive sanctions that would only stoke conflict with North Korea," he said. "Actions like that might give psychological satisfaction to some countries, but they won't help solve the North Korean nuclear crisis."

Notably, too, the Korean-language page for China's embassy in North Korea does not feature the condemnation of the test, concentrating on bright reports celebrating the two nations' friendship. (

kp.china-embassy.org/

and

kp.china-embassy.org/kor/

) (Editing by Nick Macfie and Alex Richardson)