"Burj Dubai is now taller than Taipei 101 in Taiwan, which at 508 metres has held the tallest-building-in-the-world title since it opened in 2004," Emaar Properties, which is developing the Dubai tower, said in a statement.
"Burj Dubai has now reached 141 storeys, more storeys than any other building in the world."
The developer wants the tower, set to be completed next year, to be the world's tallest building according to all four criteria listed by the Chicago-based Council on Tall Buildings and Urban Habitat, which measures buildings to the structural top, the highest occupied floor, the top of the roof and the tip of the spire or flagpole.
Emaar did not say how tall the finished building will be.
Once completed, Burj Dubai will have consumed 330,000 cubic meters of concrete, 39,000 metric tons of steel and 142,000 square meters of glass, Emaar said. It will have 56 lifts traveling at 1.75 to 10 meters per second.
The tower will be the centerpiece of a $20 billion development that will include residential, commercial and retail property.
Most of the 4,000 laborers are Indian. They toil around the clock in Dubai's sizzling summer with no set minimum wage. Human rights groups regularly protest against labor abuse in , but local media rarely report such complaints.
Dubai, the Gulf Arab trade and tourism hub, has embarked on a series of mega-projects in recent years, developing three palm-shaped islands off its coast and a cluster of man-made islands shaped like a map of the world.