A trio of superstars are set to join Serena Williams at January's ASB Tennis Classic in Auckland.

Serena's sister Venus Williams, and former world number one's Caroline Wozniacki and Ana Ivanovic are all understood to be returning to Auckland this summer.

Venus Williams and Ivanovic are former ASB Classic champions.

Wozniacki has climbed back up to 16 in the rankings after enduring a torrid start to the season and plummeting outside the world's top 50.