* 'Blew it', says Murray after throwing away 4-1 second set lead
* Williams needs only 58 minutes for victory
* Frenchman Benneteau pulls a stunner
* Second seed Halep beaten by Sharapova (Recasts, adds later matches)
Aug 15 Five times Cincinnati winner Roger Federer blunted Andy Murray's attempt at a comeback, while women's world number one Serena Williams roared to victory as they moved into the semi-finals at the Western & Southern Open on Friday.
The second-seeded Federer defeated Murray 6-3 7-5 after the Scot had taken a 4-1 lead in the second set.
Williams, bidding for her first title at the Ohio hardcourt tournament, romped to a 6-1 6-3 victory over Serbian Jelena Jankovic in just 58 minutes.
World number three Federer said he had "lost a little bit of the rhythm" before rebounding against the eighth seeded Murray in the second set.
"From the baseline, he was hitting the ball well - harder and deeper..." Federer told reporters. "I snuck in a quick break, and next thing you know, I'm back. I feel like I stole that second set."
Murray, though, thought he had blown an opportunity to get back in the match.
"Obviously I was well up in the second and blew it," he said. "It's a shame."
The Scot broke Federer in the third and fifth games of the set for his 4-1 lead. But his Swiss opponent fought back to level the set, breaking Murray twice and holding serve to pull even at 4-4. Both players held until Murray bowed out on his serve.
In the first set, Federer broke Murray for a 3-2 lead and closed out the set by breaking him again. Federer won 82 percent of his first serve points (14 of 17) and saved both break points he faced on his own serve.
"I hit the ball well," Federer said of the set. "I was the more aggressive guy out there. I was having more impact from the baseline and on the serve."
Federer will face Canadian fifth-seed Milos Raonic in Saturday's semi-finals with surprising Frenchman Julien Benneteau meeting Spain's David Ferrer in the other.
Raonic breezed past 15th seed Fabio Fognini of Italy 6-1 6-0 in a quarter-final mis-match that lasted only 57 minutes.
Benneteau delivered the day's shock with a 1-6 6-1 6-2 ousting of Swiss world number four Stan Wawrinka to reach his first Masters semi-final.
Benneteau belted nine aces and broke serve four times as he earned his second victory over a top-10 opponent this year and became the first Frenchman in 14 years to advance to the Cincinnati semis.
Ferrer outlasted fellow Spaniard Tommy Robredo 6-4 3-6 6-3 a day after Robredo, the 16th seed, had stunned world number one Novak Djokovic.
Williams needed just 25 minutes to claim the first set against Jankovic. She fell behind 2-1 in the second with an early break, but won five of the next six games, closing out the match with back-to-back aces.
"She's beaten me several times, so I knew today I just had to be focused and do the best I could," Williams said after claiming her 10th win in 14 matches against Jankovic.
"It didn't seem fast," Williams said. "I was just trying my best. And she played some great points. I was just trying to not make many errors, stay focused and do the best that I could."
The top seed wound up with as many winners as unforced errors at 22-22 while the eighth-seeded Jankovic finished made five winners and 24 unforced errors.
Williams, unsuccessful in five previous attempts at Cincinnati, will face Dane Caroline Wozniacki on Saturday for a chance to play for Sunday's title.
The other semi-final will match Russian Maria Sharapova, who edged second-seed Simona Halep, against former world number one Ana Ivanovic of Serbia.
The 12th-seeded Wozniacki upended fourth seed Agnieszka Radwanska of Poland 6-4 7-6(5).
Sharapova, seeded fifth, outlasted Romanian Halep 3-6 6-4 6-4 and Ivanovic beat Ukrainian Elina Svitolina 6-2 6-3. (Reporting by Gene Cherry in Raleigh, North Carolina, editing by Ed Osmond and Patrick Johnston)