China on Wednesday refused to let the UN Security Council publish a report on North Korea's nuclear sanctions busting, diplomats said.

The sanctions panel report calls for tougher implementation of sanctions against North Korea and outlines progress the isolated Stalinist state has made with its uranium enrichment, according to diplomats.

The report says the uranium enrichment is a new violation of UN sanctions imposed after North Korea said it staged nuclear bomb tests in 2006 and 2009.

The 15-nation Security Council on Wednesday discussed the North Korea nuclear case at a closed hearing but China again refused to allow the normal publication of such reports, diplomats said.

"Many council members are pushing for its publication on the grounds that it is important that all UN member states get access to the findings and recommendations to improve compliance," said one diplomat, speaking on condition of anonymity.

He said just one country was blocking publication and other diplomats confirmed that it was China blocking the release.

China is the North's closest ally and has sought to protect the Pyongyang regime on the international stage while seeking to restart six nation talks on the nuclear program.

Diplomats said that China's action was strange as a Chinese expert, Xue Xiaodong, has signed off on the report.

The report says North Korea has at least one secret nuclear military site, and that subterfuge work was probably started in the 1990s without raising suspicions, according to diplomats who have seen the document.

It is based on evidence from US scientist Siegfried Hecker, who was taken to a secret site by the North Korean authorities last November.

Hecker has told of seeing hundreds of centrifuges when he went to the Yongbyon nuclear complex. The report quoted him as saying North Korea must have had foreign help to build the facility, one diplomat told AFP on condition of anonymity.

The United States and other Western nations among the Security Council's 15 members have called for tougher sanctions on Pyongyang.

earlier related report
China pledges effort to revive stalled nuclear talks
Seoul (AFP) Feb 23, 2011 - China will work to revive stalled talks on North Korea's nuclear disarmament and to maintain peace on the Korean peninsula, Foreign Minister Yang Jiechi said Wednesday during a visit to South Korea.

But Yang, in comments before he began private talks with his counterpart Kim Sung-Hwan, did not mention the North's uranium enrichment programme, which has sparked international concern.

China will seek an early resumption of the talks "to realise denuclearisation of the Korean peninsula and normalisation of relations between related countries", Yang said.

The talks, which group the two Koreas, the United States, China, Japan and Russia, have been stalled since December 2008. The North abandoned them in April 2009 and conducted a second nuclear test a month later.

Seoul, Washington and Tokyo say Pyongyang should improve inter-Korean ties before the nuclear dialogue can resume.

Yang said China would work with other countries including South Korea "to pursue peace, stability and development" on the peninsula.

His visit was originally scheduled for last November but was postponed after the North's deadly shelling of a South Korean border island.

China's failure publicly to condemn the North for that attack sparked irritation in Seoul, as did its refusal to identify the North as the culprit in the sinking of a South Korean warship last March.

Minister Kim said some South Koreans "raised concerns about our bilateral relationship" following the two incidents, but that ties had improved.

South Korean officials said earlier they expected the ministers to discuss the North's uranium programme.

The nuclear-armed North last November disclosed an apparently operational uranium enrichment plant to visiting US experts, giving it a potential second way of making atomic bombs.

Pyongyang claims the programme is for peaceful energy development but experts say it could easily be converted to produce weapons-grade uranium.

Japan and South Korea have urged the United Nations Security Council to take up the issue with a view to possible punishment.

China opposes taking the issue to the world body even though President Hu Jintao has expressed concern at reports of the programme.

China has warned its Security Council partners that it intends to block publication of a report on the subject, a diplomat at the United Nations told AFP last week.

The report says the North almost certainly has at least one other undisclosed enrichment-related facility and describes the uranium programme as a serious violation of UN sanctions.

Beijing insists on the issue being discussed when six-party talks are revived.

President Lee Myung-Bak urged China to play a "constructive role" in resolving the nuclear crisis when he met Yang later, according to the presidential office.

Lee also stressed that a genuine change in North Korea's attitude is necessary for peace on the peninsula, it said.

Yang reportedly reaffirmed Beijing's objections to Pyongyang's nuclear weapons development and expressed hope inter-Korean relations would improve.