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Prime Minister Julia Gillard has told the people of north Queensland all Australians will be thinking of them as tropical cyclone Yasi bears down in the next few hours.

She delivered a simple message to affected residents on Wednesday afternoon: "In the hours of destruction that are coming to them, all of Australia is going to be thinking of them."

"Our thoughts are with you," she told reporters in Canberra.

Ms Gillard said Yasi was probably going to be the worst cyclone to hit Australia.

But before the clean-up could begin, she said people were about to face "many, many dreadful frightening hours".

Ms Gillard paid tribute to the spirit of Queenslanders, who are only just beginning to recover from devastating floods.

"(Yasi) is a powerful natural force but the courage of the people of far north Queensland is an even stronger force again," she said.

Ms Gillard said the Australian Crisis Co-ordination Committee was continuing to oversee government efforts to manage the crisis.

Following the cyclone, defence assets including helicopters, naval assets and 4000 soldiers in Townsville would be available to help.

Ms Gillard said the government would make sure Centrelink systems were up and running as soon as possible to help victims.

"But before we get to that stage there are many, many dreadful frightening hours ahead for the people of far north Queensland," she said.

"This is going to be a very difficult night."

Ms Gillard said in the hours after the cyclone, Australia would be with north Queenslanders on the ground making a difference.

"The people of Australia will be there to help the people of far north Queensland through," she said.

Ms Gillard said she had personally spoken to the local MPs who were in their communities providing leadership.

"I have also had the opportunity to speak on a number of occasions with Premier Anna Bligh," she said.

"Premier Anna Bligh and her emergency management team are facing this crisis with the same steely determination that has got them through so far."

Ms Gillard said 4,000 soldiers based in Townsville plus defence ships and aircraft were available to help once the cyclone passed.

She said the defence force had already played a significant role in evacuating hospital patients and assisting in the preparation.

"Of course the people of our defence force will continue to be there making a difference," she said.

Ms Gillard said she would visit far north Queensland at an appropriate time, depending on the process of recovery.

"The last thing anyone would want to do is to use an aviation asset that could be better deployed for immediate search and rescue work," she said.

"I will time a visit, bearing in mind that the most important thing we can do in the hours as the cyclone passes over, is get on with the task of cleanup, of search and rescue and making sure people are okay."

Ms Gillard said she would be monitoring the situation from Canberra.

The crisis co-ordination committee is meeting in the capital.

"We are linked in at every level to the Queensland government team," she said.

"I am obviously directly linked in with Anna Bligh, talking to her regularly."

She said representatives of the federal government's crisis co-ordination team as well as defence personnel will sit in on regular emergency management committee meetings Ms Bligh and her team are holding in Queensland.

"These arrangements have been very useful ones during the days of the flooding crisis," Ms Gillard said.

- AAP