An international developer has flagged plans to build what would be Perth's tallest building as the centrepiece of a World Trade Center development that it believes will transform the city's CBD.

The proposed $1.85 billion complex includes a 75-storey tower, convention centre, apartments, a mall and shopping precinct as well as a hotel and offices.

It would stretch from Stirling Street to Wellington Street, above and across the existing railway line running east from the Perth train station.

The developer, the World Trade Center Perth, has already purchased the old Myer site in Northbridge, and will negotiate with the State Government to purchase adjacent land across the rail line.

Premier Colin Barnett has backed the plan, despite earlier dismissing the concept when it was proposed for the East Perth Power Station site.

"Obviously, it's a big investment, a lot of work to be done, a lot of detail but it will be a great addition to Western Australia and a great addition to the City of Perth. So thank you for your interest and again, I assure you of the Government's support in this project," he told the developers at a launch function in Perth.

Premier Colin Barnett has backed the plan, despite earlier reservations. ( ABC News: Andrew O'Connor )

Talk of a World Trade Center in Perth emerged last year, after it was revealed Ghazi Abu Nahl, a chairman of the World Trade Centers Association, met in 2014 with the Metropolitan Redevelopment Authority (MRA) to express an interest in the East Perth Power Station site.

At that time, Mr Barnett showed no enthusiasm for the development.

"World trade centres have been around since the 70s, they are basically property developments," the Premier told the ABC at the time.

"I think we're a very international city as we are so I don't think that serves any purpose particularly."

But in unveiling its vision for establishing a World Trade Center in Perth, the developer stressed the value of the development was in international links and trade, not just in an iconic building.

World Trade Center Perth business development director Neil Kidd said the project was much more than just a "box".

"What goes in the "box? Essentially a fully integrated product to conduct trade effectively and efficiently requires each of the elements you see [in this complex] ... it has a combination of offices, malls, conferencing, parking facilities, international hotel and serviced apartments," he said.

A view of the proposed World Trade Center from Roe and Beaufort streets in Perth. ( Supplied: WA Government )

WTC chairman Ghazi Abu Nahl welcomed the opportunity to pursue the development in Perth, which he said would complete the link between the CBD and Northbridge, and connect Perth with other such centres around the world.

"The idea of the World Trade Center is not only to link (the CBD), the idea of the World Trade Center Perth is actually to link the West Australian and Perth business community together with another 330 cities all over the world."

Mr Barnett acknowledged his initial reservations about the concept, but said this concept was different.

"I think at that time there were suggestions that the State Government should help fund such a centre," he said.

"I was making the point, which is true, that its is primarily a property development, a very major one but it is also one that has international links."

Mr Barnett said he was comfortable with the imposing scope and sale of the proposed development.

The WTC Association is pursuing the land purchase through the Barnett Government's unsolicited bid process, introduced to boost its struggling asset sales program.

The developer said the negotiations would be conducted over the coming months, and if it was to proceed, the World Trade Center would be built in stages.