Obama offers Rudd help fighting deadly fires

US President Barack Obama has telephoned Prime Minister Kevin Rudd to offer his condolences over wildfires that have left at least 173 dead and offer US help in fighting the blazes, the White House said.

"The president offered his prayers to the people of Australia and his condolences to the victims. The president asked if the US could provide assistance to the government and people of Australia to assist with the fire," said Obama spokesman Robert Gibbs.

Obama telephoned Rudd immediately after holding the first press conference of his young presidency, Gibbs said in a statement.

The firestorm has engulfed entire towns in Victoria and wiped out families, triggering both heartache and anger after police revealed some were set deliberately, launching the country's largest arson investigation.

Authorities have warned the death toll, already the worst in Australia's history, would rise during the week.

And more than 30 US firefighters were reportedly flying to Australia to join reinforcements from fire departments around the country who are heading to Victoria, where the blaze began Saturday after a once-in-a-century-heatwave.