A senior engineer of the Qinghai-Tibet Railway Corporation (QTRC) said he had received no notice that the tourist train would begin running in September.
He also denied the service would be as "luxurious" as some media reported. Some reports had speculated that the "luxury train" would be reserved for overseas tourists.
"There is no detailed schedule yet, but I can confirm it won't start in September," said Li Shunping, chief engineer of the company.
QTRC announced in March that the train, with carriages on a par with a five-star hotel, would be launched on Sept 1.
Zhu Mingrui, the QTRC general manager who made the announcement, said the train would accommodate just 96 passengers. The fare would be about 20 times the normal price and also more expensive than a flight from Beijing to Lhasa.
No reason for the delay was given by QTRC, which is based in Xining, capital of Qinghai province.
Some local media speculated that the delivery time of the carriages could be a factor.
The manufacturer of the carriages, Bombardier Sifang Power, based in Shandong province, told the Qingdao Morning Post on Aug 21 that they would be delivered on schedule in February. The company was not informed that the service would be operating in September.
The newspaper report said the train would have 12 passenger cars, two dining cars and a sightseeing car.
Each passenger car would have four 20 sq m suites with double beds and bathing facilities.
Ministry of Railways spokesman Wang Yongping wrote in his personal blog recently that the train should be called a sightseeing train, rather than a luxury train.
"The biggest difference between this train and other services is the special sightseeing car, where larger windows and comfortable chairs offer passengers a better view of the scenery," he said.
The 1,956-km Qinghai-Tibet section of the rail line, running from Xining to Lhasa, which became operational in July 2006, was Tibet's first rail link with the outside world.
