Mr Libeskind, who designed the JewishMuseuminBerlin has described his collaboration with Childs as a "forced marriage", but it was all smiles at the news conference.
In 1999 his first high profile work - the JewishmuseuminBerlin - opened after 10 years construction, followed in 2002 by the Imperial War Museumin Manchester.
Mr Libeskind, who designed the JewishMuseuminBerlin, would like to keep much of the gaping hole left at the World Trade Center site for space for an eventual memorial.