RFS Commissioner Shane Fitzsimmons says there is a chance a massive bushfire could break out and move into suburban parts of western Sydney.
A significant bushfire could break containment lines and start burning through suburban areas of western Sydney if conditions deteriorate, firefighters have warned.
NSW Rural Fire Service Commissioner Shane Fitzsimmons says the 264,000-hectare Green Wattle Creek bushfire on Sydney's southwestern outskirts is a priority on Saturday.
"There is potential for the fire to break out, cross the (Warragamba) dam and move into the western suburbs of Sydney," he told reporters on Saturday morning.
"It has the potential to come out into more populated areas this afternoon."
Mr Fitzsimmons said crews have been working around the clock to contain the Green Wattle Creek blaze.
"Crews have been doing extraordinary work with backburning and the use of aircraft and machinery on the ground to try and lock that in," he said.
"That's one of our focus fires, of course, but I would say as a broader message be alert, be focused on any new fires today.
Extreme fire danger is forecast for six fire districts in NSW's southeast and the ACT, while severe conditions are forecast for Sydney, the Hunter and the central ranges.
There are some 137 bushfires burning in NSW on Saturday morning, with around 60 uncontained.
More than 3,000 firefighters are on the frontline, with 31 specialist strike teams in place across NSW.