Kerber set for 'biggest challenge' as she returns after 18 months

Germany's Angelique Kerber is unsure how she will fare when she returns to tennis following nearly 18 months out after becoming a mother.

Kerber will make her comeback at the United Cup in Australia at the end of the year.

"Of course I'm really looking forward to it," the 35-year-old three-time grand slam winner, whose daughter Liana was born in February, told dpa.

"But of course I'm also a bit nervous because I can't guess how I will perform and what it will be like."

Kerber said the comeback was the "biggest challenge" of her career.

"I'm prepared and fit enough to give myself the best chance of getting back to the level I was at. But I haven't played any matches for an extremely long time," added the former world number one.

"That will be the most difficult thing to assess. That's why I have to openly admit that I first have to find out where I really stand."

The Germans at the mixed-teams event, which also includes Olympic champion Alexander Zverev, will face Italy in their first United Cup group match on December 30 in Sydney.

"It will certainly be a bit more stressful with Liana, also in terms of the long-distance flight and the time change, but I'll try to take it easy," Kerber said.