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Rugby World Cup Minister Trevor Mallard will today unveil plans for a national stadium on the Auckland waterfront to highlight New Zealand for the 2011 Rugby World Cup and boost Auckland's goal of becoming a world-class city.

Acting Prime Minister Michael Cullen yesterday all but ruled out Eden Park as the other possible venue for the cup by saying its suburban location limited its sporting capacity and use for events such as concerts.

"It is a very constrained ground in terms of future usages."

Jade Stadium in Christchurch was third in line, with North Harbour stadium "just potentially" next, Dr Cullen said.

In a last-ditch effort to stay in the running, the Eden Park Trust Board unveiled an enhanced design rebranded as "Stadium New Zealand" to counter Government claims that Eden Park would always be an Auckland stadium and struggle for funding.

Dr Cullen said on Wednesday that a waterfront stadium might be a "national stadium" and easier for taxpayers and ratepayers to fund.

The latest $385 million plan for Eden Park has covered stands circling the park and lower rooflines on the new stands. The $320 million "legacy" option had provided new covered stands over the east terraces and south stand but left the uncovered west stand for future development.

Eden Park development committee chairman Rob Fisher said he had known for some time of the Government's preference for a waterfront stadium but he had not been told officially of a decision. It remained to be seen whether "we have been knocked out of the race".

"The issue is not what they prefer, it is what can be built in time and at a reasonable cost. We will still maintain that Eden Park is the viable option that can be completed on time. Even the second option at $385 million is going to be way, way less expensive than anything the Government can do at the waterfront," Mr Fisher said.

The preferred waterfront site is over Marsden Wharf between Captain Cook and Bledisloe wharves.

The site is across the road from the Britomart transport terminal, close to buses and ferries and a 90-second walk from the bottom of Queen St.

It is understood the stadium, about 35m high, would face out to sea.

It has been designed by Wellington architectural firm Warren and Mahoney, which designed Wellington's Westpac Stadium.

One source who has seen the plans said it was clad in a translucent material or glass, included harbour views and was "simply spectacular". Another source said it looked like any other stadium and was nothing to rave about.

A waterfront site has divided design experts. Institute of Architects president Ian Athfield said it was important it fitted into its environment, while Sky Tower architect Gordon Moller said it would wreck the waterfront.

Today's announcement will be made in an upper floor of a building overlooking the waterfront.

Ports of Auckland chief executive Geoff Vazey said he had yet to see a stadium proposal that could be built in time, and Auckland Regional Holdings chairwoman Judith Bassett said there were serious risks from a stadium anywhere on port land. Regional Holdings, the investment arm of the Auckland Regional Council, owns Ports of Auckland.

National sport spokesman Murray McCully, who has been briefed by Mr Mallard and asked to support enabling legislation, said National was looking to be co-operative but still needed more information.

The Green Party strongly opposes a waterfront stadium and Auckland list MP Keith Locke has written to Mr Mallard complaining about the Government's lack of consultation.