Firefighters are working to link two out-of-control fires burning in the NSW Blue Mountains in an effort to starve them of fuel and prevent a "mega-fire" forming.
Rural Fire Service Commissioner Shane Fitzsimmons says firefighters are backburning at fire grounds at Lithgow and Mt Victoria to try to join the two fire fronts.
He says the convergence is aimed at containing the two blazes and stopping them linking up with a third uncontained fire at Springwood.
"There is work going on at the moment to try and tie in the eastern edge of those fires bringing them together," Mr Fitzsimmons told reporters at RFS headquarters on Tuesday.
"They will do it on their own but the containment strategies will seek to link those two fires together."
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There are 63 fires burning across the state, 13 of them uncontained.
The huge State Mine fire at Lithgow is at "emergency" level while the fires at Springwood and Mt Victoria are at "watch and act".
A fire at Balmoral in the Southern Highlands is also at "watch and act" level, the RFS advises.
Mr Fitzsimmons said the backburning operation in the Blue Mountains would hopefully prevent all three fires merging into a "mega-fire".
"The work ... by all these firefighters and these teams over recent days has given us the best prospects of avoiding that situation occurring," he said.
Backburning was about 80 per cent "locked in" around the towns of Bilpin and Berambing in the Blue Mountains, Mr Fitzsimmons said.
"They (firefighters) have had some extraordinary success ... but there's still a way to go," he said.
He said firefighters were trying to surround the two fires at Lithgow and Mt Victoria ahead of higher temperatures and stronger winds forecast for Tuesday and into Wednesday.
"We can expect to see those winds strengthen up to 60 to 90 km/h, which is what we're trying to prepare for and brace for," Mr Fitzsimmons said.
In addition to the fires, there were "large tracts of the state" that remained at risk and under total fire bans.
The RFS said around 1100 firefighters were battling blazes across NSW overnight.
Fire and Rescue NSW has ordered one of the largest mobilisations of fire engines and officers in its history, sending up to 170 tankers and 800 officers to the Blue Mountains.
