Treasurer Josh Frydenberg has warned the government's promised budget surplus could evaporate due to the economic fallout from the nation's bushfire emergency.

As the Business Council of Australia gave its blessing to the government running a budget deficit if that meant delivering much-needed assistance to communities and businesses, Mr Frydenberg said it was still unclear the economic damage caused by the fires.

The government is promising a $5 billion surplus for the 2019-20 financial year, the first surplus since 2007-08.

Australian Defence Force personnel assist the ABC to restore broadcasting services by clearing bushfire debris around a tower.

In its mid-year budget update, released before fires ripped through much of southern NSW, parts of Victoria and South Australia, Mr Frydenberg was forced to downgrade expected surpluses over the next four years due in part to the impact of drought.