Kim Clijsters' Australian Open preparations took a severe knock on Wednesday when the world number two was forced to hobble away from her Hopman Cup match against Alicia Molik.

Her retirement, while leading 6-3, 6-7, 3-2, almost certainly destroyed plans for the eagerly-awaited "love match" in the mixed doubles where she was due to face fiancé Lleyton Hewitt for the first time later in the day.

But, more importantly, it cast a dark shadow over her plans for the opening Grand Slam of the year later this month.

The Belgian baseliner was forced to quit after she appeared to injure her Achilles during the match at the ITF mixed team competition.

At the changeover while leading 3-2 in the third set, Clijsters had her left ankle strapped and looked in pain as she put weight on it.

Moving gingerly in the next game, she managed just two more points before hobbling to the net to tell her opponent she could not continue.

Clijsters left the court immediately without speaking to the on-court interviewer.

There was no immediate official comment as to her condition, but for a player whose game is centred on her speed and mobility, any type of injury spells bad news.

Having lost in the final of three grand slams -- twice at the French Open and in the 2003 U.S. Open -- Clijsters had high hopes of breaking her duck heading to Melbourne Park.

She has been training hard with Hewitt under the Australian sun during the off-season and had looked in great shape just days before the Open.

Her participation in next week's Sydney International, the final warm-up tournament, must now be in doubt.

The first slam of the year kicks off at Melbourne Park on January 19th.