Scott Morrison says defence personnel stand ready to assist firefighters battle the bushfires raging in NSW and Queensland.
But addressing reporters outside Kirribilli House in Sydney, the prime minister also issued a sombre warning.
"Sadly, we have lost two Australians and I fear that we will lose more before the day is out," Mr Morrison said.
Two people have died and seven people are missing as fires in NSW destroyed at least 100 homes amid warnings of worse to come, while thousands of evacuated residents in Noosa, Queensland are waiting to hear whether their homes are safe to go back to.
In an earlier tweet, Mr Morrison described the bushfires as "simply terrifying", while Labor Leader Anthony Albanese said their ferocity is "unimaginable".
"Our main thoughts and our prayers are with those who have been so directly and horribly impacted by these fires," Mr Morrison told reporters on Saturday.
"I want them to be assured ... that their governments will be doing everything they can, not just to relieve them from this immediate situation, but to be there in the recovery in the weeks and the months and years ahead."
Mr Morrison said he had been in talks with key cabinet ministers during the morning.
These included Deputy Prime Minister Michael McCormack, Deputy Nationals leader Bridget McKenzie, Natural Disaster and Emergency Management Minister David Littleproud, and Defence Minister Linda Reynolds.
The prime minister said the Australian Defence Force has presented options on call outs of reservists "as may be necessary", but stressed they are not trained firefighters.
"The ADF can provide a lot of support in logistics and other activity, and will, as required," he said.
Mr McCormack told reporters in the Riverina, NSW the situation is "very, very worrying".
He said for the more than 100 homes that have been destroyed, the government will act under emergency procedures with regards to financing for those people who are now homeless.
"Those people will not be left without shelter. Those people will not be left without cash," he said.
Mr Morrison expected disaster recovery payments would be operational over the weekend and would mean $1,000 for individuals and $400 per child.
In a joint statement with Labor's own natural disaster and emergency management spokesman Murray Watt, Mr Albanese said the loss of lives is "heartbreaking" for the families and communities affected.
"We pay tribute to our incredible emergency personnel and volunteers for their brave efforts to protect their fellow Australians," they said.
"You have the nation's gratitude. We cannot thank you enough."
Greens spokesman for the climate crisis Adam Bandt in a statement said he was "deeply saddened" by the loss of life.
But he turned on Mr Morrison, saying he "bears some responsibility" and must apologise to the communities impacted.
"Scott Morrison has not got the climate crisis under control," he said.
"Let me be clear. I'm not saying the prime minister is directly responsible for the fires and the loss of life, but he has contributed to making it more likely that these kinds of tragedies will occur."