Tennis world number one Novak Djokovic said yesterday he was not certain he would be able to play for Serbia in 2012 Davis Cup due to his "packed agenda," Beta news agency reported.

Djokovic has already said he would skip the first round of the Davis Cup match with Sweden to be played in southern Serbian town Nis on 10-12 February in order to get some rest from the busy season.

"I am sorry that I will not play against Sweden in Nis... I can not promise that I will take part in this competition this year," Beta quoted Djokovic as saying.