Its ruler, Sheik Mohammed bin Rashid Al Maktoum, famous for breeding and racing thoroughbred horses and for his $US18 billion ($24 billion) fortune, was due to give it his blessing at a VIP launch.

The complex will provide homes and offices for 100,000 people. If all the reinforcing bars were laid end to end they would stretch a quarter of the way around the world.

The tower will be so tall it will have five microclimates. The temperature in the atmosphere at the top could be as much as 10 degrees cooler than at the bottom. Lifts will allow people to see the sunset twice - from the bottom and again from the top.

Developers in Saudi Arabia and Kuwait will doubtless take note.

Dubai, once a sleepy fishing and pearling port, is home to some of the biggest and busiest shopping malls on the planet, as well as indoor ski slopes in a desert country where the temperature is regularly more than 40 degrees.

Nakheel is famous for its signature Palm Jumeirah island and is building two other offshore developments that will extend Dubai's 70-kilometre coastline to 100 kilometres. Next month Kylie Minogue will inaugurate Jumeirah's huge $US1.5 billion Atlantis hotel, where guests can pay $US25,000 a night for a room and gaze at sharks in a vast aquarium in the lobby.

The port and harbour complex has been announced to loud fanfare. But key questions remain unanswered, not least its cost at a time of tightening credit, falling oil prices and sharemarkets, and a sense the Gulf is not immune to the world financial crisis.

"We all know the world is experiencing incredible market movement," Mr O'Donnell said. "This will have an impact on the Middle East, but our view is that it will be relatively small. This will be built over 10 years. I can guarantee we will have many more cycles over this period."

Nakheel was keen to stress that the design includes Islamic elements inspired by the Alhambra in Spain, the harbour of Alexandria in Egypt, the promenade of Tangier in Morocco, and the bridges of Isfahan in Iran.

That looks like a gesture to Arabs and Muslims uncomfortable with the influx of expatriates to this most globalised of Middle Eastern cities, where more than 80 per cent of the population of 1.3 million are foreigners.

The message that Dubai has a vision is not new, even if the circumstances are changing for the worse. "We have been bombarded with the tallest, the best, the largest for the past few years," said Professor Abdelkhaleq Abdullah of Emirates University. "The novelty has gone."

He added: "Doom and gloom about Dubai has been around from day one; they say we are overambitious, that we are stretching our reserves, that there will be a crash. There will be a crash one day, but not yet. The leadership is amazingly confident. Still, I wish there would be a slowdown because we cannot sustain this double-digit growth."

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