Melbourne, Feb 16 : American 23-time Grand Slam champion Serena Williams on Tuesday reached the semi-final of the 2021 Australian Open after beating Romanian world No.2 Simona Halep in straight sets at the Rod Laver Arena. Williams beat Halep 6-3, 6-3 to set up a semi-final clash against Japanese third seed Naomi Osaka. This is Williams's 40th Grand Slam semi-final as she looks to equal Margaret Court's record haul of 24 career victories in majors. It is also the first time the 39-year-old, the seven-time Australian Open champion, reached the semi-final at Melbourne Park since she won the tournament in 2017. In men's singles, Russian qualifier Aslan Karatsev continued his dream run by beating Bulgarian 18th seed Grigor Dimitrov 2-6, 6-4, 6-1, 6-2 and reaching the semi-final. Karatsev will face either Serbian world no.1 and defending champion Novak Djokovic or German sixth seed Alexander Zverev in the semi-final. Earlier, Osaka eased into the semi-final with a straight sets win over South Korea's Hsieh Su-Wei. The three-time Grand Slam champion, seeded third in the tournament, beat Hsieh 6-2, 6-2. This is the first time since she won the tournament in 2019 that Osaka has reached the semi-finals at the Australian Open. She has gone on to win a Grand Slam every time she reached the semi-finals. /IANS