Two of Britain’s leading architects today unveiled their plans to remake the New York skyline with crystalline skyscrapers rising side by side on the site of the World Trade Centre.

Lord Foster of Thames Bank will plant diamonds in the sky above Manhattan with a sloping roof, divided into four, atop his 78-storey office tower at Ground Zero.

Lord Rogers of Riverside picked up the motif with diamond-shaped structural braces running up the sparkling side of his adjacent 71-storey tower, right across the street from the planned World Trade Centre memorial garden.

Designs for the two skyscrapers, along with a third by Japan’s Fuymihiko Maki, were made public today as part of a renewed push to rebuild the 16-acre site five years after the September 11 terror attacks.

The three architects rushed to get their conceptual designs done within a four-month deadline, working cheek by jowl on the 25th floor of 7 World Trade Centre.

"It was a great experience. I did not think it would work in the beginning, but it worked brilliantly," Lord Rogers told The Times. "The last time I did it was when I was at Yale with Norman Foster in 1961 in school."

The three skyscrapers form part of a five-tower ensemble spiralling up to the site’s signature 1,776ft high Freedom Tower designed by David Childs - a homage to the date of America’s declaration of independence.

Lord Foster, who designed the "Gherkin" Swiss Re Building in the City of London, explained that he had sheared the roof of his 1,254ft cruciform tower so that it angles down towards the planned Memorial Garden below.

"The skyline of New York for me is inseparable from these iconic buildings The Chrysler Building, the Empire State," he said. "The pinnacle of this building is in that tradition."

Lord Rogers, the architect of London’s Millennium Dome and Paris’s Pompidou Centre, said that he wanted his 1,155ft Ground Zero building to be "legible" so that the public could see how it was built.

It will have a three-level glass lobby with a "big picture window" right onto the planned World Trade Centre Memorial. He said he would do further "modelling" of its roof.

The unveiling offered some relief for New York’s frayed nerves ahead of Monday’s fifth anniversary of the attacks. In a poll published today, 69 per cent of New Yorkers said they were "very concerned" about another attack - down only slightly from 74 per cent in October 2001.

The rebuilding of the World Trade Centre site, where 2,749 people died, has been plagued by disputes among developers, architects and government officials as well as protest by victims’ families upset about the planned memorial.

The mayor of hurricane-ravaged New Orleans touched a raw nerve for New Yorkers last month when he defended his own reconstruction efforts by pointing out that, five years on, the World Trade Centre site remained a "hole in the ground."

So far, the only structures built at Ground Zero are an unexceptional 52-storey glass replacement for 7 World Trade Centre - which collapsed on the evening of the attack - and a temporary commuter train station.

Tourists have had to be content peering through a steel fence at the sprawling building site - although a temporary visitor centre is to open next week with exhibits such as a chunk of one of the hijacked airliners.

Although the foundation stone of the Freedom Tower was laid amid great fanfare on July 4, 2004, it later had to be moved aside to accommodate design changes made to protect the base from a possible car bombing.

Government officials stepped in to take over building the Freedom Tower in April because of fears that the leaseholder, Larry Silverstein, would not have the funds to build all five planned skyscrapers on the site.

The deal left Mr Silverstein in charge of three of the skyscrapers, allowing construction of the Freedom Tower finally to start. All five skyscrapers are scheduled to be completed by 2012.

The planned memorial, featuring waterfalls running into square voids where the twin towers once stood, has also had difficulties. It is now due to open in 2009, but only after officials ordered a drastic redesign eliminating underground chambers to cut the projected $1 billion cost by half.

The state-sponsored Lower Manhattan Development Corporation, which oversaw the entire site, has, meanwhile, announced that it is closing its doors.

Its disappearance leaves a question mark over funding for a planned $50 million performing arts centre to be designed by Frank Gehry that is to host New York’s Signature Theatre Company and Joyce dance theatre.

"There are still many challenges ahead, many issues to be addressed, many time-lines to be met, before we can start patting each other on the back,", Sheldon Silver, the powerful chairman of the New York State Assembly, observed at yesterday’s unveiling ceremony.

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