The revised plan features a heavily reinforced concrete core, steel bars on every floor and a lobby set back from the street and draped in protective panels of titanium and stainless steel, designers said.
The Freedom Tower, the proposed centrepiece of the rebuilding at the site known as Ground Zero, was sent back to the drawing board in May due to police concerns that the building would be too close to street traffic to protect it from the threat of a car or truck bomb.
"There's no question that this is a huge symbol," said James Kallstrom, former FBI chief in New York who is overseeing security plans.
"Terrorists have attacked it two times before. It would be naive of us to think they wouldn't try again."
Gov George Pataki, who with mayor Michael Bloomberg and others unveiled the new design at a Manhattan news conference, said he was so confident in the building's safety that he would be "honoured" to have one of his children work in it.
The attacks of September 11, 2001, when two hijacked jets slammed into the World Trade Centre, killed 2749 people. A bomb attack in 1993 killed six people.
Police Commissioner Ray Kelly said in a statement he approved of the new design, which he said would better "protect the building against bomb blasts..."
The footings of the building are scheduled to be laid in the first quarter of next year, and completion is set for 2010.
Seventy floors are designed for occupancy.
Like the earlier plan, the new Freedom Tower will be 541 metres tall to symbolise the year the United States declared its independence.
Sides of the slender new building are sliced into eight faceted triangles, four pointing up and four down, so at its midpoint it is octagonal, said architect David Childs.
Its roof will be 415 metres and the parapet 417 metres - the heights of the two fallen twin towers, he said.
It will be set back an average of 27.5 metres from nearby West Street. The earlier set-back was 7.6 metres. Other safety measures include stairs and sprinklers encased in a core that is three feet thick in most places.
30 June 2005 - Fairfax New Zealand Limited