Aus Open: Federer dispatches Berdych to meet Chung in semis

Defending champion Roger Federer argued with an umpire but mostly let his racket do the talking as he beat Tomas Berdych for the ninth time running to reach the Australian Open semi-finals on Wednesday.

Despite the 7-6(1), 6-3, 6-4 scoreline, it was not all smooth sailing against the burly Czech for the 36-year-old Federer as he arrived in the last four of a grand slam for the 43rd time -- and the 11th time without dropping a set.

Federer trailed early on, but 19th seed Berdych faltered when serving for the first set at 5-3 when Federer was infuriated by the malfunction of the Hawkeye video replay.

Berdych had one set point which Federer saved with a sweetly-struck backhand and another backhand went past him to give the Swiss the break back.

Second seed Federer turned on the style in the tiebreak, allowing Berdych a solitary point, and then wrapped up the second set with a single break of serve.

Berdych could have thrown in the towel when he fell behind in the third set, but kept Federer on his toes by breaking back.

It only delayed the inevitable, though, as Federer broke again and completed the job with a love service game to set up a meeting with South Korean sensation Chung Hyeon for a place in the final.

The 21-year-old world No 58 is the lowest ranked player into the last four at Melbourne Park since Marat Safin in 2004.

Chung Hyeon's trailblazing run through the Australian Open continued on Wednesday as the South Korean tossed American Tennys Sandgren aside 6-4, 7-6(5), 6-3 to become his nation's first Grand Slam semi-finalist.

Bespectacled like Clark Kent but playing like Superman at a sunbathed Rod Laver Arena, world number 58 Chung became the lowest ranked player into the last four at Melbourne Park since Marat Safin in 2004.

The 21-year-old wobbled when serving out the match, squandering a 40-0 lead and seeing a total of five match points disappear into a cloudless sky as world number 97 Sandgren battled gamely.

But his raw power ultimately prevailed, a blazing forehand into the corner causing a scrambling Sandgren to push his desperate retrieve well past the baseline.

Tennys Sandgren of the United States reacts during his quarter-final match against South Korea's Chung Hyeon at the Australian Open on Wednesday.

"I don't know, in the last game at 40-0, I thought it was time to do a ceremony or something like that," Chung told Jim Courier in the on-court interview.

"After the deuce break point, no ceremony, just keep focused."

Chung will meet the winner of Roger Federer for a place in the final, and will be full of confidence after another hugely impressive display in his break-out Grand Slam.

He showed great composure to come back from a break down in the second set, after Sandgren belatedly found some energy after a heavy-legged opening set.

Chung, who became the east Asian nation's first Grand Slam quarter-finalist by toppling six-times champion Novak Djokovic in the previous round, acknowledged thrilled South Korean fans draped in flags in the terraces and the TV audience back home.

"To all my fans, friends back in Korea. I'm not done yet. See you on Friday," the muscular tyro said on court as his delighted parents beamed in the players' box.