NSW Premier Gladys Berejiklian made the announcement on Thursday in Sydney, saying lead contractor Laing O'Rourke would be obliged to engage local contractors in bushfire-affected communities.

"We hope the bulk of the clean-up will be done by the end of June. We know that's an ambitious target but we're confident most people will feel some type of relief, assistance by that time," Ms Berejiklian told reporters.

"We know what confidence it engenders in the community when the clean-up starts."

Federal Treasurer Josh Frydenberg said the average cost of a clean-up site was about $50,000, with the cost rising if hazardous materials are involved.

Almost 2400 homes have been destroyed in NSW to date this bushfire season, with another 263 facilities and 5263 outbuildings razed.

Ms Berejiklian said the clean-up commitment was separate to the NSW government's $1 billion pledge to rebuild bushfire-damaged infrastructure.

"We're unfortunately still in the middle of the bushfire season so in some parts of NSW the recovery can begin. In other parts it's still subject to fire threats and of course, when you're talking about rebuilding infrastructure, you need to make sure you do that when it's safe to do so," Ms Berejiklian said.

Ms Berejiklian also said the clean-up effort may necessitate the creation of new landfill sites around NSW.

Prime Minister Scott Morrison said in a statement the clean-up agreement would help provide certainty to those affected by bushfires.

"We know many people are still battling these blazes but where the fire front has passed we're deploying $2 billion through our National Bushfire Recovery Agency to help people rebuild their homes and communities," Mr Morrison said.

Australian Associated Press