London: Prince William and his wife Catherine are set to visit bushfire-ravaged Australian coastal towns during a special royal visit that will spur more international financial support for survivors and volunteer firefighters.

Preliminary negotiations between the Morrison government and Kensington Palace – the Duke and Duchess of Cambridge's official household – have been under way for weeks and Prime Minister Scott Morrison is expected this week to issue the formal invitation needed to clear the way for the tour.

The Duke and Duchess of Cambridge are set to visit Australia in their second visit as a couple. Credit:Phil Noble

The trip will be William's fifth visit to Australia and the pair's first since 2014. William, second in line to the throne after his father Charles, toured flood-stricken Queensland and Victoria on behalf of the royal family in 2011.

The couple have been distressed by the death toll, destruction of thousands of homes and widespread loss of flora and fauna during the summer disaster. They quickly expressed interest in visiting, but did not want to divert resources to a royal tour in the immediate aftermath of the emergency.