Sir Rod Stewart has been forced to cancel a concert due to a viral illness.

The 78-year-old singer was due to perform at the Mt. Duneed Estate in Geelong over the weekend, for 'A Day On The Green' as part of his Australian tour, but had to pull out just hours before the gig.

Six hours before his show, a message on Rod’s Instagram stated: "Live Nation and Roundhouse Entertainment regret to announce that tonight's performance by Rod Stewart, Cyndi Lauper and Jon Stevens at Mt. Duneed Estate, Geelong will not go ahead due to illness,' his statement read.

"We are sorry for the disappointment and inconvenience for ticket holders. A further announcement regarding the concert arrangements will be made early next week."

Rod later told fans that he was suffering from a viral infection.

He wrote on Instagram: "Hello my friends. I'm absolutely downhearted that I'm disappointing my friends who bought tickets to 'A Day On The Green'. Late this morning, I was advised that I have a viral infection and my throat is too irritated to sing. I'm only human and sometimes get sick like you do. My greatest joy is performing for you, so I'm doing everything I can to get on the mend and back on stage."

Rod's tour, which also features Cyndi Lauper and Jon Stevens is scheduled to take in Queensland and New South Wales, with the final two shows set to take place in Hunter Valley on April 1 and Bowral on April 2.