"It's because of all the concern in the media and on the Internet, the government is a little wary and has slowed down the process," said Zhang Yue, the chairman of the Broad Group.
But he vowed to finish the building, saying that he expected a delay of no more than two to three months, with completion of the building in June or July next year instead of the original plan of finishing it in April. Workers have already dug a large hole in the ground for the foundations and have just laid a four-lane road to the site to bring in heavy equipment.
"No matter how high the obstacles, I will for certain overcome them to make sure this project is completed," Mr. Zhang said. He declined to identify who in Beijing had delayed his project, but said that he had not been asked to make any adjustments to the design.
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David Scott, a prominent structural engineer in London who has worked on many extremely tall buildings, said that regulatory delays were a periodic problem for such projects all over the world, but could usually be overcome.
Local officials here say that while they have transferred the land for Sky City to Broad Group and have been installing electricity and water lines for the project, final approval for the project is still "in progress" from building safety experts in Beijing.
The blueprints for Sky City call for a stack of long, skinny rectangles that taper to a narrow top, like a very tall and angular wedding cake. It bears a blocky resemblance to the 110-story Willis Tower in Chicago, formerly the Sears Tower, which was the world's tallest building until 1998 but is now being left in the shade by numerous rivals.
Beijing, Shanghai, Shenzhen, Guangzhou and Chongqing, each similar in population to metropolitan New York, are now finishing one building apiece that will top the Willis Tower.
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Wuhan, the size of greater Houston, is erecting two buildings taller than the Willis Tower and Tianjin, the size of metropolitan Chicago, is constructing three, according to the Council on Tall Buildings and Urban Habitat, the Chicago nonprofit that tracks skyscraper bragging rights.
Ambitious local officials, together with state-owned companies and state-owned banks, stand behind most of these projects, raising fears that taxpayers may eventually pick up the bill if projects prove uneconomical.
"If you let the market decide, I don't think a lot of these tall buildings would proceed," said Chau Kwong Wing, a professor of real estate and construction at Hong Kong University. Despite public concerns, there is no sign so far that any of the many very tall buildings under construction in China has been canceled by regulators in Beijing, he and Mr. Zhang both noted.
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Sky City is the most ambitious project of all, and so it has become the lightning rod for criticism of the trend. Chinese media have been openly skeptical about the project, questioning its safety, construction speed and the wisdom of relying on prefabricated modules.
But work nonetheless continued earlier this month at the site. Bulldozers sliced slabs of earth and six drilling rigs bored holes for a drainage system.
Mr. Zhang said in an interview at his headquarters here on Aug. 7 that he had all the approvals needed to start work, and he and other executives said that it was common in China to keep working pending further approvals.