The world No 32 cited a left wrist injury as the reason for her withdrawal.
Venus Williams survived a scare before beating Danish teenager Caroline Wozniacki while Virginie Razzano got the better of Italian Flavia Pennetta in the semi-finals of the Japan Open.
Madison Keys continued to ride her wave of success, fuelled in part by celebratory chocolate biscuits, as she advanced to her first Grand Slam semi-final with a gutsy 6-3, 4-6, 6-4 victory over Venus Williams on Wednesday.
Halep withdraws from Western & Southern Open with injury.
The former world number one beat Japan's Akiko Morigami 6-1, 2-6, 6-4 in the first round of the Memphis International.
Defending champion Venus Williams eased into the third round of the Dubai Championships on Tuesday with a 6-2, 6-3 victory over Germany's Sabine Lisicki. Top seed Caroline Wozniacki had to recover from 1-5 and save a set point to defeat Slovak Dominika Cibulkova 6-2, 7-6 while second seed Svetlana Kuznetsova received a walkover when Spain's Anabel Medina Garrigues withdrew with a back injury.
Five-times champion and second seed Venus Williams was stunned 6-2, 6-3 by Bulgaria's Tsvetana Pironkova in the quarter-finals of Wimbledon on Tuesday.
According to reports, the couple married at the Contemporary Arts Center in New Orleans with select few.
China's Li Na defeated a battling Venus Williams 7-5, 3-6, 6-1 to reach the final of the Cincinnati Open on Saturday after an enthralling two-hour nine minutes encounter.
She beat sixth seed Ana Ivanovic in the first round of the Luxembourg Championship on Wednesday.
The Williams sisters Serena and Venus fell by the wayside in the fourth round at Wimbledon on Monday. Defending champion Serena was beaten 6-3, 7-6 by Frenchwoman Marion Bartoli while five-time champion Venus was outplayed by Bulgaria's Tsvetsana Pironkova 6-2, 6-3.
Ekaterina Makarova, who upset an injured Serena Williams in the fourth round of the 2012 Australian Open, completed a Melbourne Park sweep of the Williams sisters by eliminating Venus 2-6, 6-4, 6-4 to advance to the second round on Monday.
Third seed Venus Williams's return to Canada ended in a shock 1-6, 7-5, 6-4 second-round defeat by Ukrainian qualifier Kateryna Bondarenko at the Toronto Cup on Tuesday.
France's Marion Bartoli upset American Venus Williams 6-2, 5-7, 6-4 to win the Stanford Classic on Sunday.
Flavia Pennetta stunned Venus Williams with an impressive 6-4, 7-6 win to reach the Bangkok Open final.
Third seed Venus Williams found herself on the brink of defeat before rediscovering her touch to beat Czech Lucie Safarova 6-7, 6-2, 7-5 and reach the third round of the French Open on Thursday. The American, who saved a match-point in the 10th game of the decider, will next face Hungary's Agnes Szavay, seeded 29th.
Fourth seed Venus Williams retired from her Australian Open third round match against Germany's Andrea Petkovic with injury on Friday after lasting just seven points.
Venus Williams, playing her first tournament since returning from an autoimmune disease, continued her inspiring comeback at the Sony Ericsson Open on Sunday.
Williams sisters Serena and Venus had been hoping to provide fans with the first all-Williams sisters clash at a Grand Slam since the 2009 Wimbledon final in the semi-finals.
Nadia Petrova lost 6-3, 6-3 to Italy's Mara Santangelo in the second round of the Warsaw Cup.
Venus Williams continued her quest back to the top of women's tennis on Wednesday, upsetting fourth seed Patty Schnyder to reach the third round of the Amelia Island championship.
The French Open has not produced a lot of happy memories for Venus Williams in recent times, but now that she's reached the third round for the first time in six years, the American hopes her 2016 adventure won't come to an abrupt end.
Venus Williams won her second match in two days at the season-ending WTA Championships on Wednesday when she beat Elena Dementieva 6-4, 4-6, 6-3 to leave herself on the brink of the semis with one round-robin match to play. Russian Vera Zvonareva also remained undefeated after a 6-3, 6-7, 6-4 victory over Serbia's Ana Ivanovic in the white group.
Venus Williams unleashed the fastest serve by a woman at a grand slam as the American kept the Stars and Stripes fluttering at the French Open on Wednesday.
A display of raw desire over a decade ago from sister Serena inspired Venus Williams to ascend the summit of the women's game but there will be no room for sentiment when the siblings meet for the fourth time in a Wimbledon final on Saturday.
Top seed Caroline Wozniacki and former World No 1 Venus Williams ensured Auckland Classic organisers' dream final remained on track with the duo both recording comfortable victories in their first round matches on Tuesday.
Venus Williams is a two-time mixed doubles winner at Grand Slams, triumphing at the Australian Open and Roland Garros in 1998.
The 27-year-old American beat France's Marion Bartoli 6-4, 6-1 in the final.
A big serve to the backhand side clattered off the racket of third-seeded twice champion Venus Williams and the Belgian, returning to the grand slam stage after more than two years away, had a 6-0, 0-6, 6-4 win and a spot in the quarter-finals.
A nagging knee injury has forced Venus Williams to skip the rest of the 2010 tennis season, including next month's Fed Cup final between the United States and Italy.
Injured Venus Williams will join her sister Serena on the Fed Cup sidelines with Vania King named to take her place on the US team that will play the quarter-finals in Antwerp against Belgium.
Top seed Maria Sharapova dodged the showers on her way to a 6-3, 6-2 victory over Taiwan's Chan Yung-Jan to set up a third round encounter against Venus Williams at the Sony Ericsson Open on Saturday.
The American has targeted a return to the world's top 16 by the French Open.
The former champion has withdrawn from the U.S. Open with a lingering stomach muscle injury.