Pataki called for a new design, citing security concerns raised in recent weeks by the New York Police Department.
Certain details, such as the 1,776-foot height and the 276-foot spire, are expected to remain, according to an official familiar with the plan.
WTC master site planner Daniel Libeskind originally envisioned the height to symbolize the year of American independence and the spire to evoke the arm of the Statue of Liberty in New York Harbor.
The building will be similar with exception of the first 150 to 200 vertical feet , said Charles Gargano, vice chairman of the Port Authority of New York and New Jersey, which owns the land.
A government official said the tower will still be "an iconic building" that "retains some of the concepts" envisioned by Libeskind and the tower's lead architect, David Childs.
Another government official said, however, that "there will be some significant changes."
To conform with police concerns, the building will be set back farther from West Street, a multilane highway that runs along the west side of the 16-acre site.
Instead of 25 feet from the street, the tower will be "three times" as far, Gargano said.
The base is being redesigned using new security standards, Gargano reported. It will have a smaller "footprint" and be more of a square than a parallelogram.
The tower will still occupy the northwest corner of ground zero.
A 20-ton granite cornerstone was laid last July. Pataki wanted the tower's steel frame to be completed in 2006 and ready for occupancy in 2008. But that timetable is already delayed.
