Harare — THERE is no stopping Zimbabwean tennis ace Cara Black at the on-going US Open in New York.

Black is fighting from two fronts at this year's US Open. She is playing in the women's doubles and the mixed doubles competitions.

In the women's doubles, Black is partnering American Liezel Huber and the co-world number ones and defending champions are already through to the semi-finals of this year's competition.

Black is also the defending champion in the mixed doubles where she is combining forces with Indian ace Leander Paes -- the man who partnered her to victory in last year's final at Flushing Meadows.

And after reaching the mixed doubles final of this year's fourth Grand Slam with Paes on Tuesday, Black hogged the limelight again on Wednesday night when she pulled through to the semi-finals of the women's doubles with Huber.

Black and Huber made it into the last four of the women's doubles after beating the Spanish duo of Nuria Llagostera Vives and Maria Jose Martinez Sanchez in the quarter-finals, according to reports from New York.

In a battle that lived up to the hype, number one seeds Black and Huber, who have five WTA Tour titles this year, out-clasted sixth seeds Llagostera Vives and Martinez Sanchez.

The third set was on serve all the way through until Black and Huber broke Martínez Sánchez's serve at 5-5, and then Black served it out for the 6-3, 2-6, 7-5 victory.

Black and Huber are now 6-0 in the career series between the two teams, but they split sets in the last three matches, including in the quarters of Wimbledon earlier this summer.

Black and Huber's semi-final foes today will be number three seeds Samantha Stosur and Rennae Stubbs, both of Australia.

In Wednesday's other quarter-final, fourth-seeded Serena and Venus Williams were tested, but got past 11th-seeded Yan Zi and Zheng Jie of China, 7-5, 6-4.

The Williams sisters, who are now 2-1 against the Chinese duo, actually lost their first encounter with them, in the quarter-finals of the 2008 Australian Open, before getting revenge with a double bagel in the round of 16 at Wimbledon this year en route to the title. The Williams, who have yet to drop a set in this tournament, next play 13th-seeded Russians Alisa Kleybanova and Ekaterina Makarova in the semis.

Meanwhile, Black's partner in the mixed doubles, Paes, rekindled his love affair with the US Open on Wednesday as for the second year running, he made it through to two doubles finals at Flushing Meadows. There is something about Arthur Ashe Stadium that brings out the "A Game" in Paes.

And on Day 10 of the hardcourt major, he punched away a volley to secure a 6-4, 3-6, 7-6 win with his men's doubles partner Lukas Dlouhy to knock out top seeds Bob and Mike Bryan.

"This crowd is just magic, I hope you show up again," the 36-year-old Paes told the fans after raising his fists in celebration.

He won less than 24 hours after reaching the mixed doubles showpiece with Zimbabwe's Black.

Twelve months ago Paes suffered mixed fortunes in the finals when he and Black went on to pick up the trophy but he faltered with Dlouhy in the men's doubles showpiece.

On Wednesday, the Indo-Czech pair steamed to a 5-1 lead in the deciding tiebreak only to see the Americans wipe away the advantage.

After watching five match points vanish, Paes made no mistake on the sixth and left the Bryan twins flat-footed as he sent a volley flying through the middle of the court.