Andy Murray is set to miss this year's World Tour Finals if, as expected, Belgium decide to host the Davis Cup final against Great Britain on clay.
The Flanders Expo Arena in Ghent will stage the tie if the Davis Cup Committee gives its approval on Tuesday.
The Belgian Federation has two weeks to confirm its choice of surface, but has opted for clay in four of its last six home ties and may conclude it is the surface most likely to inconvenience Murray.
The World Tour Finals - on a hard court - finish at London's O2 Arena on Sunday, 22 November, with the Davis Cup final played over three days from the following Friday.