In a brief statement published late on Friday, the Swiss company said Peter Brabeck-Letmathe had been diagnosed with a curable illness and would need periodic medical treatment over the next six months.

The 69-year-old Austrian is also chairman of motor racing business Formula One.

The Vevey-based firm said the board of directors had been informed of Brabeck-Letmathe's illness on Thursday. A spokesman declined to give further details on what the illness was.

"This does not affect Mr Brabeck-Letmathe's ability to carry out his role as chairman of the Nestle Board of Directors and he will continue to fully exercise his duties during the treatment period," Nestle said.

Brabeck-Letmathe served as chief executive of the maker of KitKat chocolate bars and Nespresso portioned coffee from 1997 until 2008.

He said in a newspaper interview published last week that he would step down as chairman in 2017.

A keen climber and skier, Brabeck has also campaigned to goad world leaders into action to try to avert a looming crisis over water supplies.

(Reporting by Caroline Copley; Editing by Anthony Barker)