MELBOURNE (Reuters) - Jason Day has been forced to withdraw from the World Cup of Golf and Australian Open next month due to a lingering back injury, the world number one has said.

Day had been scheduled to play the Australian Open at the Royal Sydney Golf Club from Nov. 17-20, then partner world number six Adam Scott in the World Cup tournament at Melbourne's Kingston Heath from Nov. 23-27.

Day and Scott won the last World Cup event in 2013, which was also held in Melbourne, with Day clinching the individual title, but the 28-year-old was told to rest completely until next season after tearing a ligament in his back.

"I regret that I will be unable to come home to Australia this year," Day said in a statement on Friday.

"I was looking forward to playing in the Australian Open and teaming up with Adam Scott on one of my favorite courses Kingston Heath the following week at the World Cup in Melbourne.

"My plan is to return home to Australia in 2017."

Day's injury forced him out of the PGA Tour's season-ending Tour Championship during the second round in Atlanta last month. He also withdrew during the final round of the BMW Championship in his previous event.

"It's unfortunate to lose Jason from the Australian team for this event," said Executive Director Matt Kamienski.

"But Jason's long-term health should always remain the priority. With some rest in the coming months, we hope that Jason will be back on the course at 100 percent and that we will see him in Australia in 2017."

Players from 28 countries will compete at the World Cup of Golf, which has returned to a 72-hole stroke play, two-man team event format.

The first and third days of competition will be the foursomes (alternate shot) format and the second and final days are fourball (best ball) play.

(Writing by Greg Stutchbury in Wellington; Editing by Peter Rutherford)