A bid to build the world's tallest building is facing a backlash from the public amid safety concerns that the building will be erected in a record seven months.

Broad Group, the investor behind Sky City, to be built in Wuhan, capital of Central China's Hubei province, published an open letter to address public concerns about safety.

At Saturday's foundation stone laying ceremony, which is expected to be the world's tallest building with 208 floors and a total height of 838 meters, brought the long running controversy into the spotlight again.

The world's current tallest structure is the 829.8 meters tall Burj Khalifa in Dubai, United Arab Emirates.

Sky City is estimated to take an unprecedentedly short period of seven months to construct, but this is not counting the time to lay the foundation. In contrast to the building time of 5-10 years for most skyscrapers, the short construction process triggered concerns that completing such a project in such a short time may cause potential safety hazards.

In the open letter on its official website, Broad Group said the construction is quick because 90 percent of the building is made from pre-fabricated units produced in factories, while only ten percent involves on-site construction works. The units will be produced by 20,000 workers in four months. Then it will take three months for 30,000 workers to finish fabricating the units and other actual constructions on site.

In response to concerns over the tower's ability to withstand strong earthquakes, wind and fire, the letter said the Sky City adopts a stable pyramid style and bundled tubes design, and it uses sturdy Luxembourg H steel beams, all of these ensure the building could withstand a magnitude-9 earthquake. What's more, the design passed the anti-earthquake evaluation by Chinese authorities.

The letter also said the steel beams were covered with fireplates. Tests show the building can withstand fire for more than three hours. And the building passed three wind tunnel testings from foreign research institutes, which prove its wind-resistant abilities.

A spokesman from the Broad Group said they will answer public questions at a news conference to be held before the fabrication process.