Venus Williams came through an entertaining quarter-final with Francesca Schiavone to make the last four of the US Open.
The third seed and home favourite defeated her Italian opponent 7-6 (7-5) 6-4 on Flushing Meadows' Arthur Ashe court.
Schiavone, seeded sixth, was the underdog going into the match but was full of energy and regularly found her best shots just as Williams looked to be taking control.
There were two breaks apiece in the first set, leading to a thrilling tie-break that saw French Open champion Schiavone at her most vocal as she berated herself for the missed opportunities that allowed Williams to go ahead.
Two-time champion Williams looked she might make life easier in the second set when she broke Schiavone in the fourth game then served out the next to go 4-1 ahead.
But Schiavone, backed into a corner, came out fighting and took the next two games.
It had looked as though she had missed her chance to break back when she failed to convert a pair of chances at the net with the score at 30-40, but she held her nerve to put the pressure back on Williams.
In a match characterised by strong return games and loose serving Williams immediately added another break of her own meaning at 5-3 she had the chance to serve for a a place in the last four.
What followed was a tame attempt which culminated in a big double fault.
With the possibility of another tie-break looming, Schiavone dropped serve for a fifth time to see Williams into a semi-final against number two seed Kim Clijsters.
Clijsters struggled to a 6-4 7-5 6-3 victory over fifth seed Sam Stosur to set up the last-four match with Williams.
There were 15 breaks of serve in a match littered with errors from both players but as the game reached its climax, the Belgian finally found some composure to hold off Stosur, who should have cashed in on Clijsters' sluggish opening.
Clijsters started particularly poorly, yielding an early break and contributing several unforced errors in the opening games.
Despite looking the more assured, Stosur could not add a second break and the slowly improving Clijsters moved to level the scores at 4-4 before taking a second of Stosur's service games on her way to clinching the first set.
Stosur broke her opponent as soon as the second set began but could not hold on as Clijsters returned the favour to put the scoring back with serve.
A shoddy service game from Clijsters, including two double faults, gave Stosur a 5-4 lead and the chance to serve for the set only for yet another break to delay what eventually became a 7-5 win for the Australian.
The pair continued to make scores of mistakes as they broke each other on a virtually routine basis in the third set - the first six games all going against serve.
But it was Clijsters who finally got her game in order, stringing together three consecutive games to take a 6-3 triumph.