Milder overnight conditions in New South Wales have helped Australian emergency crews fortify fire containment lines near Sydney. They are still battling 80 blazes across the state, as the bush fire crisis enters its third week. Extremely hot and windy conditions are expected within the coming days, which could hamper containment efforts.

The main hot spots remain in the Blue Mountains to the west of Sydney, and coastal regions to the south. Authorities say what are called "back-burning" efforts, when fires are deliberately set to create buffer zones, have been successful in the mountains.

Milder weather conditions overnight have helped these efforts to stop the advance of the flames.

But the outlook for the next 48 hours could worsen the situation. The forecast is for higher temperatures and westerly winds that bring hot, dry air from the arid interior.

Fatigue is now a major problem among the 20,000 mostly volunteer emergency workers battling the bush fires.

The New South Wales Fire commissioner, Phil Koperburg, says the strain is beginning to show "Its our job to manage that fatigue, of course; and sometimes we succeed, and sometimes we dont quite succeed. But, yes, theyre getting weary. Even if they are confined to their normal shift arrangements that is a number of hours on and a number of hours off, which varies considerably depending on what theyre doing of course even when that is maintained, there is fatigue beginning to set in," he says. "What we have to guard against is that fatigue leading to something more serious."

Aerial water-bombing efforts will be boosted in the coming days, with the expected arrival of two more giant American helicopters, which will join the one already serving in New South Wales. Nicknamed Elvis, the heli-tanker can drop 9,000 liters of water at a time. The two new helicopters are expected to arrive in Sydney on Monday.

Australian police believe more than half the fires were started deliberately. Twenty-six people have been arrested on suspicion of arson. The premier of New South Wales, Bob Carr, is supporting the proposal of several local councils for a register of convicted arsonists to be set up.