Chinese officials said on Thursday that the preparations for the 18th Party Congress, which will formalise the leadership transition, were currently on-going, but continued to be guarded about the dates of the meeting amid growing speculation about a possible delay.

“The preparations for the 18th Party Congress are well underway,” Foreign Ministry spokesperson Hong Lei told reporters, adding that authorities would release information “in due course”.

At the congress, which will see sweeping changes across all levels of the leadership, Communist Party of China (CPC) General Secretary Hu Jintao is set to be replaced by Vice President Xi Jinping. Mr. Xi, along with Vice Premier Li Keqiang who is expected to succeed Wen Jiabao as Premier, will be the only members of the nine-member Politburo Standing Committee who will retain their positions.

Mr. Hong declined to comment on rumours regarding the health of Mr. Xi, who, last week, cancelled meetings with visiting U.S. Secretary of State Hillary Clinton and Singapore Prime Minister Lee Hsien Loong on September 5. U.S. officials said they were told that Mr. Xi had a back problem.

Media reports this week suggested he was suffering from a more serious ailment as he did not appear in public on Monday at a reportedly scheduled photograph session with visiting Danish Prime Minister Helle Thorning-Schmidt.

However, Chinese sources said there was no such meeting planned, with the Danish Prime Minister only scheduled for meetings with officials at the State Council, or cabinet. The Danish government has also suggested that no meeting with Mr. Xi had been included in the initial schedule.

Mr. Xi's last public appearance was at the Central Party School on September 1, where he delivered a speech. It is, however, common for Chinese leaders to not make public appearances for long periods of time for various reasons. In July, all members of the Standing Committee were not seen in public for more than a week, when discussions over the transition were taking place at the seaside resort of Beidaihe.

State media on Thursday said Mr. Xi and other top leaders had offered their sympathies to the family of a retired official from southern Guangxi who died last week. President Hu Jintao and Mr. Xi had “expressed their grief and heartfelt sympathies”, the report said.

While it appeared to suggest that the leadership was functioning as normal, it did not release any photographs, adding further grist to the rumour mill.

Two Chinese analysts said whatever ailment Mr. Xi may have, indications were that it was not serious enough to derail the party congress. This was reflected in recent overseas trips made by senior leaders that suggested business was as usual.

Media reports have variously suggested that Mr. Xi sustained a back injury while swimming, or alternatively suffered a mild heart attack or stroke. “Whatever is coming out is all rumour, and the fact is that nobody really knows,” said the political analyst. “That has always been the case with the senior leaders' health.”

More outlandish rumours suggested that Mr. Xi and anti-corruption chief He Guoqiang were targeted in staged car accidents. The rumour, put out by a U.S.-based Chinese language website, was reported widely by international media outlets, but proved to be wide off the mark when Mr. He appeared in public on Wednesday.

Mr. Xi is expected to make a public appearance along with other senior leaders at a national day reception at the Great Hall of the People on September 29. If the Vice President has not appeared in public by then, the analyst admitted that questions would certainly be raised about the transition.

“If it is a mild ailment, there will be no impact whatsoever,” the analyst added. “If it is something serious, it could complicate matters,” suggesting that the equations that determine on-going bargaining for top positions might change.

The Congress will not only determine the composition of the next Politburo Standing Committee, but also its size. Proposals to reduce the size of the body to seven, from nine, are being considered.

Allies of Mr. Hu, with backgrounds in the Communist Youth League, and officials with ties to former President Jiang Zemin, who also enjoys close relations with Mr. Xi, are pushing for a position on the all-powerful body. Whether or not Mr. Xi will immediately replace Mr. Hu as the head of the Central Military Commission is also, as yet, unclear. Mr. Jiang held on to the post for two years after stepping down as President.

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