But it does believe both are important pieces of infrastructure for Perth's future.
WA Treasurer Mike Nahan said that after more than $20 million worth of planning since 2008, Roe 8 " the first stage of the |$1.6 billion effort to link Roe Highway to Fremantle Port " was good to go.
"We have a design, we have a route, we have EPA approval and now we have Commonwealth contribution to it and we're getting on with the business," he said.
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READ NOWFremantle MLA Simone McGurk, among others, has called for the freight link to be scrapped and work to begin on the outer harbour.
"I think the better solution is to get on and start planning the outer harbour and to take freight away from communities and into an industrial area. That's a solution for the 21st century. That's where we should be putting our infrastructure dollars," she said.
Mr Nahan said a new harbour could cost between $3-$5 billion.
Transport minister Dean Nalder said there were serious environmental concerns associated with a potential harbour in Cockburn Sound.
"People are thinking the environmental work has been done. I had it confirmed (Tuesday) " with the EPA that it would be a minimum of three years of environmental work that needs to be undertaken,� he said.
�The estimated time I�ve had on construction from my department is it would take six to seven years to construct the outer harbour.
"So we're talking a minimum of 10 years."
Mr Nalder said Fremantle Port could accommodate doubling freight movements but the outer "overflow" harbour would be needed.
Cockburn Mayor Logan Howlett said a container park at Latitude 32 in Wattleup was a better option than the freight link.
He said he had support from Fremantle and East Fremantle councils.
"The intermodal facility at Latitude 32 is essential and the outer harbour can flow from that," he said.