Despite calls from heritage and preservation groups to keep the 21ft-high 'survivors' stairs' in their original position, it now appears the structure will need to be removed from its current home.
According to developer Larry Silverstein, there is no way the staircase can be incorporated into Foster's plans for a 78-storey tower on the site of the original Twin Towers in New York.
The National Trust for Historic Preservation has been battling to keep the staircase, which was used by hundreds of people to escape from the burning buildings, as a memorial to those who died on the September 11 2001.
Although there are plans to ship the stairs to another location, the trust wanted the structure to remain in its current position and listed it among America's most endangered historic places.
Meanwhile, Foster continues to face opposition from a gaggle of historical groups across the city who have come out against his Madison Avenue proposals.
At the last count almost 60 groups had aired views against the skyscraper scheme on the city's Upper East Side.