Rory McIlroy to play South African Open

Rory McIlroy has kept his promise to Ernie Els and will play the South African Open in January.

Rory McIlroy has been forced to withdraw from the Dubai Desert Classic because of a rib injury. (AAP)

Rory McIlroy is set to play in the South African Open in January, with organisers saying he'll keep a promise he made to tournament host Ernie Els.

Els said McIlroy owed him one after the South African appeared at the Irish Open in 2014.

World No.3 McIlroy will return after playing the South African Open as a newly-turned professional in 2008.

The four-time major winner is part of the Europe team for the Ryder Cup, which starts Friday. He won the PGA Tour's FedEx Cup last weekend with victory at the Tour Championship.

The South African Open is one of golf's oldest national opens and goes back more than 100 years. The 2017 tournament, part of the European Tour, is on from January 12-15 at Johannesburg's Glendower Golf Club.