By Simon Evans

MIAMI (Reuters) - Kim Clijsters won a dramatic semi-final battle of the Belgians against Justin Henin to reach the final of the Sony Ericsson Open on Thursday.

Clijsters dominated the opening set of her encounter with Henin but then, having been 3-0 up in the second, lost out in a tiebreak to allow the game into a decisive third set.

Neither of the two former world number ones, who have both made comebacks to the game, dominated on serve and Clijsters produced a double fault when serving for the match.

After losing the first two points of the tiebreak, Clijsters roared back to take a 6-3 lead but once again Henin refused to roll over.

She won the next three points to close to 6-6 before Clijsters produced two great shots -- a volley close to the net and then a forehand across the court -- to win the match.

Henin praised Clijsters for coming up with the big shots at the right moment.

"It wasn't a great match but she played better on the important points," said Henin. "She was more aggressive and took the opportunities and I think that really made the difference."

Clijsters also won on a tiebreak the last time the pair met in the final of the Brisbane Open in January.


"It was a very, very similar game and it is pretty crazy to have two matches like that with each other so early in the year," said Clijsters.

"It's a good win but now I am focusing on Saturday, there won't be any celebrating whatsoever, the tournament is not over," she added.

The tall blonde faces on a confident Williams, whose victory over Bartoli was watched from the stands by her injured sister Serena.

"I think a lot is going to come down to the serve," said Clijsters, "I have to go out and play aggressively again."

Seven-times grand slam winner Williams was not at her sharpest but still proved too good for out-of-sorts 13th seed Bartoli.

The American broke serve straight away in a first set containing plenty of errors from both players.

After her opponent broke back, Williams responded with a second break thanks to three double-faults.

Bartoli then looked poised for a second-set comeback after breaking to go 3-1 up but Williams broke back immediately with a spectacular cross-court forehand volley and then broke again to clinch victory.

Venus has won the event three times but her last appearance in the final came nine years ago, when she beat Jennifer Capriati.

"I'm really happy to be back in this final and obviously I want to take it a step further," she said.

(Editing by Nick Mulvenney and Alastair Himmer)