US Open PHOTOS: Serena hands Navarro double bagel

Defending champion Serena Williams walloped Spain's Carla Suarez Navarro 6-0, 6-0 to race into the semi-finals of the US Open on Tuesday.

Top seed Williams served up the dreaded 'double-bagel' in a quickfire 52 minutes to set up a clash with fifth seed Li Na, who earlier became China's first US Open semi-finalist by beating Russian Ekaterina Makarova.

"Honestly she's a great player," said Williams, blaming windy conditions for the Spaniard's plight on her 25th birthday.

"The conditions today were so tough. It was not her best tennis today."

The outcome may have been more about the World No 1 being at something close to her best, however.

Williams won 88 percent of her first serves, rifled in four aces, smacked 20 winners to three for her opponent, and won 53 points to just 18 for the 18th seed.

"I played really good. I was just more focused than anything," she added, stopping short of calling it her best. "I like to believe there is room for improvement."

It was only the second love-love victory in a US Open women's quarter-final dating back to 1968, and first since Martina Navratilova subjected Manuela Maleeva of Bulgaria to the same embarrassment in 1989.

At 31, Williams is campaigning to become the oldest US Open women's winner since tennis turned professional in 1968.

She has lost just 13 games from her five matches so far and said she has been balancing fun with work at Flushing Meadows.

"I'm having a blast this week," said Serena, who is also still alive in women's doubles with older sister Venus.

"I have just really been enjoying my matches. For me, I have to stay in that moment of fun, but intensity, but calm. If I can try to do those three things, it works out."

Suarez Navarro's consolation was a $325,000 check for being eliminated from her first US Open quarter-final.

"I just want to go there and enjoy, but Serena was playing really, really good. I do everything I can," she said.

The Spaniard, who had ousted eighth-seeded Angelique Kerber of Germany in the fourth round, said the blustery conditions had made her task even more difficult.

"Serena is a strong player. When I play with the wind against me, I have no chance," said Suarez Navarro, who had hoped to rebound after the lightning-quick, 19-minute first set.

"I was thinking the situation can change, another set is a new set. But obviously, no."

Li Na broke another barrier for Chinese tennis, becoming China's first semi-finalist at the US Open by beating Russian Ekaterina Makarova 6-4, 6-7(5), 6-2.

The 31-year-old, fifth-seeded Li pumped both fists in joy after 24th seed Makarova sailed a backhand long to end the two-hour, 20-minute match at Arthur Ashe Stadium as the crowd showered her with cheers.

"For me, this is the first time to come to the semi-finals, so I'm very proud of myself," said Li, who looked about to claim victory in two sets after winning the first three points of the tiebreaker and holding a 4-2 lead.

"After I lose the second set, I was sad. But I just told myself to go point by point."

The US Open was the last Grand Slam where Chinese women had stalled before reaching the final four.

Zheng Jie was the first Chinese player to reach a Grand Slam semi-final, making the last four at Wimbledon in 2008 and the Australian Open in 2010, but Li has enjoyed even greater success.

Two years ago, Li became the first Chinese to make a Grand Slam final when she finished runner-up in Australia and a few months later she won the 2011 French Open to become China's first Grand Slam champion.

"I will lie down in the bed, take some chips and watch the match," Li said about scouting her next opponent. "They will just fight and I'll relax."

Li took the fight to Makarova in her quarter-final, smashing 44 winners against just 15 for the more defensive 25-year-old Makarova, though the Chinese struggled with eight double faults.I will lie down in the bed, take some chips and watch the match

Meanwhile, order was restored after Monday's shocking straight sets, fourth-round surrender by Roger Federer to Tommy Robredo.

Men's top seed Novak Djokovic was dazzling in a 6-3, 6-0, 6-0 demolition of unseeded Marcel Granollers of Spain to reach the quarters.

 "Today, the second and third set have been some of the best tennis that I've played on Arthur Ashe in my career," said Djokovic, which is saying something given his charge to the title in 2011 and runs to the final in 2007 and 2012.

"I was wishing to be more aggressive as the tournament progresses and to be able to stay committed to play every point, to win every point, regardless of what's the score," said the Serb, who won the first 25 points on his serve.

"So I'm very happy with my mental state, how I feel physically, and the way I played. It's definitely coming at the best possible time."

Djokiovic will go against 21st-seeded Russian Mikhail Youzhny, who ended the run of 2001 winner Lleyton Hewitt 6-3, 3-6, 6-7 (3) 6-4, 7-5.

Youzhny, the 21st seed, out-battled renowned fighter Hewitt by overcoming deficits of 1-4 in the fourth set, and 2-5 in the fifth, as he won the last five games of the match.

"Obviously, it could have gone either way," said 32-year-old unseeded Hewitt, who had upset sixth-seeded former champion Juan Martin del Potro in the second round and was trying to reach the US Open quarter-finals for the first time in seven years.

"There were a lot of momentum changes. In the end, he played the big games when he needed to."

Switzerland's Stanislas Wawrinka powered through a high-quality match against Czech Tomas Berdych to also reach the quarter-finals.

The ninth seed beat Berdych 3-6, 6-1, 7-6(6) 6-2 in two hours and 47 minutes at Louis Armstrong stadium.

Wawrinka, who has had to live in the shadow of compatriot Roger Federer back home, was blown off the court by Berdych in the first set, but in a match featuring superb ball striking and a combined 68 winners, Wawrinka's consistency proved the difference against the fifth-seeded Czech.

He closed out the match by breaking Berdych's serve for the sixth time to move into a quarter-final against Britain's defending champion Andy Murray or Russia's Denis Istomin.

"It's always tough to play against Tomas," Wawrinka said.

"He always puts you under pressure. I'm just really, really happy. Tonight is a night I will never forget."

Defending champion Andy Murray ground his way past Uzbekistan's Denis Istomin with a 6-7(5), 6-1, 6-4, 6-4, victory to also reach the quarter-finals, where he will face Switzerland's Stanislas Wawrinka.

Briton Murray struggled to get out of the blocks in the first set and trailed 5-3 after two forehand errors handed Istomin the break.

Although Murray immediately broke back, he lost out in the tiebreak, with a double fault and a slice into the net allowing Istomin to serve out the set.

After levelling the match, the Scotsman displayed some clear signs of frustration in the third set but finally took control by breaking Istomin in a marathon seventh game after the enterprising Uzbek had saved three break points.

There was never any doubt from then as the Wimbledon champion wrapped up the match in a little over three hours.

Murray said the cool and slightly gusty conditions in Arthur Ashe Stadium were a factor in his slow start to the night match.

"It was definitely tough. It's pretty breezy out there. Quite a strong breeze. Both of us were struggling with our timing early on," he said.

"I thought we played some entertaining points. Sometimes when it's windy like that, you get some fun points.

"I just started trying to dictate the points. I tried to use my forehand a little bit more," he added.

Victoria Azarenka booked her place in the quarter-finals earlier on Tuesday when she beat Serbia's Ana Ivanovic 4-6, 6-3, 6-4 in an error-strewn fourth-round match.

Azarenka dropped her opening set for the second match in a row but fought her way back to win after more than two gruelling hours on a windy Arthur Ashe stadium.

"Ana just came out firing, she played amazing tennis in the first set ... ripping winners and serving great," Azarenka said in a courtside interview. "I really had to wake up in the second set.

"In the second set, I felt I was determined, more focused and taking more opportunities."

The Belarussian's next opponent is unseeded Slovakian Daniela Hantuchova, who beat American wildcard Alison Riske on Monday to reach her first quarter-final at Flushing Meadows in over a decade.

Azarenka's round of 16 clash with Ivanovic was also meant to be played on Monday but was postponed until Tuesday after a five-hour rain delay forced tournament organisers to cancel dozens of matches.

Conditions at the US National Tennis Center were not much better on Tuesday with Azarenka and Ivanovic both struggling with their serves in the gusting winds.

World number two Azarenka had her serve broken seven times and committed nine double faults, while Ivanovic lost nine of her service games and made eight doubles after making a flying start.

The match was still in the balance with the players locked at 3-3 in the deciding set when Azarenka, who made the U.S. Open final last year, seized control.

She held her own service game then broke Ivanovic again when the former world number one sent a backhand wide.

She squandered two match points on her own serve before a desperate Ivanovic broke back but closed out the match in the following game on her fourth match point when the Serbian dumped a backhand into the net.

"The match points were pretty bad," Azarenka said. "I really didn't go for my shots, I kept waiting for mistakes and something to happen."

Frenchman Richard Gasquet saved a match-point and survived a barrage of heavy shots from Canada's Milos Raonic before booking a spot in the quarter-finals.

Raonic thumped 39 aces past Gasquet but the eighth seed waited for his opportunities, winning 6-7(4), 7-6(4), 2-6, 7-6(9), 7-5 after an exhausting slugfest that lasted four hours and 40 minutes.

Raonic also hit a staggering total of 102 winners but paid the price for coughing up unforced errors, more than twice as many as Gasquet.

The 27-year-old Frenchman is a consistent performer on the professional circuit since 2002 but this is just the second time he made it to a Grand slam quarter-final.

The only other occasion was when he made the Wimbledon semi-finals in 2007.

His opponent in the next round is Spanish fourth seed David Ferrer, who advanced after a hard-fought 7-6(2), 3-6, 7-5, 7-6(3) win over Serbia's Janko Tipsarevic.