New York, Sep 13 (DPA) Comeback girl Kim Clijsters, in a controversial win, thrashed the frustrated defending champion Serena Williams 6-4, 7-5 to power into the final of the US Open.

The match ended in unorthodox fashion Saturday, with the furious Williams calling for a foot fault to yield a match point to the Belgian. Williams then exploded at a line judge to draw a point penalty and the loss.

In the last game, the American got into an altercation with a line judge who called the foot fault and was eventually assessed a second code violation - she got her first by smashing a racket after losing the first set - to end the match on a sour note.

Williams was warned for cursing the lineswomen, with tournament referee Brian Early called to the court, thus marking a bitter end.

'She was called for a foot fault, and she said something to a line umpire which was reported to the chair,' said Early, 'That resulted in a point penalty for unsportsmanlike conduct that happened to be on the match point.'

Williams tried to play down the incident.

'Today was tough, I didn't play my best, I had more errors today than all my matches combined. Kim played really well and came out with a big plan.

'I don't have any regrets, I was out there, I fought and tried. I did my best. I'm intense and give 200 percent in everything I do. I just go for it,' Williams said.

Clijsters, who stepped away from the game for more than two years for marriage and motherhood, will play the New York final Sunday night four years after her last appearance at Flushing Meadows when she won the title, her only Grand Slam crown.

She will face Danish ninth seed Caroline Wozniacki, who beat fellow teenager Belgian Yanina Wickmayer 6-3, 6-3.

Clijsters was in shock after the bizarre ending. 'I was trying to focus on the match point.

'As I started to get ready for return, I saw Serena talking to lineswoman.