Halep was ruthless in her quarter-final on Wednesday against Estonian Anett Kontaveit, needing just 53 minutes to run out a 6-1 6-1 winner.

The Romanian will take on Spanish star Garbine Muguruza on Thursday at Rod Laver Arena for a place in Saturday's championship decider.

The 28-year-old lost the 2018 title match at Melbourne Park to Caroline Wozniacki in a three-set heart-breaker but credited that defeat with giving her the belief that she could win grand slams.

Four months later Halep claimed the French Open and then last year the Wimbledon crown when she crushed seven-time champion Serena Williams 6-2 6-2 in the final.

The world No.3. said she felt she was playing at the same level against Kontaveit as she did in that match against Williams.

"Yeah, I feel like I'm there," said Halep, who is coached by Australian Darren Cahill.

"I felt really, really good on court - I felt like my game was great.

"Perfection doesn't exist, but I'm very happy with the way I played."

Halep is through to the final four without dropping a set and says she has a lot more energy than at the same point two years ago when she reached the final.

In the third round then, Halep survived a marathon three-set match against American Lauren Davis that went to 15-13 in the third.

"It's the opposite this year," she said.

"I feel with more energy going to the semi-finals - I feel more confident."

The forecast for Melbourne Park on Thursday is 37C but Halep felt well-equipped to handle the heat.

Cahill rejoined Halep after taking last year off to spend more time with his family and the pair changed up her off-season training and headed to Dubai, with the results evident on court.

Kontaveit didn't play that badly - only making 15 unforced errors - but Halep hunted down every ball and sent it back with interest.

After a cool start to the Open, she looked forward to the heat.

"I like to play in warm conditions and I feel ready to face this weather," Halep said.

"Actually we missed a little bit of the hot weather here in Australia so we will see tomorrow, but I think it's a good thing for me."

Australian Associated Press