For years now, it has seemed a foregone conclusion that One World Trade Center, the skyscraper that has arisen on the site of the destroyed twin towers in Manhattan, would rise to a symbolic height of 1,776 feet and dethrone Chicago's Willis Tower as the nation's tallest building.

But with the 12th anniversary of the Sept. 11 terrorist attacks approaching Wednesday, new twists in the arcane game of measuring skyscraper height have raised the unlikely — and, for some, unthinkable — possibility that One World Trade Center won't be No. 1 and that Willis would retain the coveted titles of the tallest building in the United States and the Western Hemisphere. The widely recognized arbiter of skyscraper bragging rights, the Chicago-based Council on Tall Buildings and Urban Habitat, will consider in November whether to knock more than 400 feet off One World Trade Center's official height, owing to a technical distinction between spires and antennas.

Such a call would disrupt the calibrated symbolism, envisioned by ground zero master planner Daniel Libeskind, of a tower rising to 1,776 feet — a reference to the year the Continental Congress adopted the Declaration of Independence and an expression of U.S. resolve in the wake of the Sept. 11 attacks.

'It's the wrong call'

"I think the common perception and the common wisdom … is that it's 1,776," said Nina Libeskind, the architect's wife and spokeswoman. "I don't know how one suddenly dictates that it isn't because they don't consider antennas to be part of the building. I would say it's the wrong call."

According to the tall building council's rule book, spires can be counted in a tall building's height but broadcast antennas, like flagpoles, are superfluous add-ons. In 1996, that distinction doomed the bid of Willis Tower, then known as Sears Tower, to retain the world's tallest building crown. Instead the council ruled in favor of the Petronas Towers in Malaysia.

Yet even if the council's height committee rules in One World Trade Center's favor, another technicality could upset the tower's appeal to national pride. Four years ago, the council revised its rules to state that a skyscraper's height is measured from the lowest significant, open-air pedestrian entrance to the building's top.

'The most significant entrance'

Because One World Trade has a secondary, north-facing entrance that is 5 feet lower than its main, south-facing entrance, the tower's height in feet could be 1,781. That hardly has the same patriotic ring as 1,776, though it would recognize the year of the decisive Revolutionary War battle at Yorktown. "The issue is not just about the height of the building. It's about the base of the building," said Antony Wood, the council's executive director.

Addressing the issue of the lower secondary entrance, a spokeswoman said the architecture firm's hope is that the design will be grandfathered in because it was unveiled in 2005 — four years before the council made its rule change. "The 'front door' … symbolically and practically, is the south entrance," Skidmore, Owings & Merrill said in its e-mail. "This is the entrance that faces the 9/11 memorial and is, therefore, the most significant entrance to the building from every standpoint."

The skyscraper's website already touts it as the tallest in the Western Hemisphere and "New York's global icon." One World Trade Center measures 1,368 feet to its roof. Its 408-foot mast stretches its height to 1,776 feet.