West Australian Premier Colin Barnett says his Government would be prepared to accommodate asylum seekers from Nauru, ahead of the closure of the Manus Island Detention Centre in Papua New Guinea.

The state Liberal leader has weighed in over the fate of asylum seekers on Nauru, amid renewed concerns about conditions on the island.

The Federal Government has repeatedly ruled out resettling refugees from offshore processing centres.

But Mr Barnett said if the Commonwealth changed its mind, his state would be prepared to accept asylum seeker families.

"The answer to your question is that particularly for families, as long as they don't present a security or safety risk, I do welcome them being in Australia," Mr Barnett told the ABC's Lateline program.

"The one thing I find unacceptable is children in detention."

Mr Barnett stopped short of demanding the Federal Government reconsider its position.

"I wouldn't call on the Federal Government but if they decide to do that we would certainly accommodate a number of them [asylum seekers] in Western Australia and we'd certainly support them as a state government."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 12 minutes 48 seconds 12 m Interview: Colin Barnett, WA Premier

Pressure mounts for Coalition to find third settlement country

Immigration Minister Peter Dutton has confirmed the Manus Island detention centre in Papua New Guinea will close but has not outlined a timetable for when that will happen.

"I just don't want to define [the timetable]," he said.

"I'm hoping it can happen as soon as possible but it's an issue for the PNG Government to work through and we'll support them in that decision."

He flagged assistance to help PNG resettle those in the facility but was adamant they would not come to Australia.

The Federal Opposition has called on Mr Dutton to provide more information about the support Australia will provide to the 800 men who are still in the facility.

Shadow immigration minister Shayne Neumann said the Government needed to be upfront about the final cost to taxpayers.

"He said it would be a substantial amount of money, he hasn't revealed that information," Mr Neumann said.

"We'd like the minister to tell us how much is a substantial amount of money.

"We need to know and the Australian public needs to know because these are taxpayer dollars."

Mr Neumann also called on the Government to fast-track resettlement negotiations with a third country and to engage more closely with the United Nations High Commissioner for Refugees.

"These people have been languishing in indefinite detention for more than three years."

Manus Island condemned by human rights lawyers

Daniel Webb from the Human Rights Law Centre spent last week on Manus Island and said the centre was a "dead end policy arrangement" that was destined to produce "nothing other than human suffering and destined to collapse".

"I spent the whole of last week interviewing these men who have been there for three years," he said.

"I met a range of people — a guy who knows seven languages, someone else who used to work for the UN, a range of people, range of ages from different parts of the world.

"What they all have in common is after three years of fear and violence and limbo.

"They are exhausted and I think it is well and truly time to bring them here. But the minister and the Federal Government say that can't and won't happen."

He noted there have been three deaths in the three years since Manus was reopened.

"Resettlement in PNG is not safe or viable — if it was it would have happened three years ago," he said.

New Zealand has a long-standing offer to accept some asylum seekers from Australia but Mr Webb said the Government should take responsibility itself.

"Rather than sort of prowling around the region looking for whether there is some other countries we can pay off to take this issue off our hands, the best, the safest, the humane and the most viable way forward is the most obvious one."