Sharapova, making her return to top-flight tennis after serving a doping ban, defeated Romanian Halep 6-4, 4-6, 6-3 to move into the 2nd round of the final major of the year.
Frenchman Jo-Wilfried Tsonga has withdrawn from the US Open due to a long-term knee problem, the United States Tennis Association said on Monday.
US Open champion Carlos Alcaraz has become the youngest world number one since the ATP rankings began in 1973.
Japan's Nishikori was the first man representing an Asian country to break through to a Grand Slam final at the 2014 tournament before Marin Cilic stopped him in the title match.
'We love our sport but it puts everything into perspective'
The US Open kicks off on August 31 and will be held in its usual home in Flushing Meadows, Queens, but will be played without fans in attendance to limit the spread of the virus.
Novak Djokovic beat Daniil Medvedev in the US Open final to win a 24th Grand Slam singles title and equal Margaret Court's record haul.
Osaka battled on gamely before retiring while trailing Kaia Kanepi 7-6(4), 3-0.
Williams came tantalisingly close to equalling the mark having reached the final in four majors since she returned from maternity leave in 2018.
Medvedev moved a step closer to a potential semi-final showdown with Novak Djokovic at the Australian Open warm-up event.
IMAGES from Day 7 of the matches played at the US Open at Flushing Meadows on Sunday.
Wimbledon finalists Novak Djokovic and Roger Federer are on a semi-final collision course at the US Open after they were placed in the same half of the draw.
Indian Wells organisers said on Tuesday that world number two Novak Djokovic had been placed in the tournament's draw but it was unclear if the Serbian would be permitted to enter the United States.
Off-court distractions and a neck injury could not prevent Novak Djokovic from extending his winning run this year to 23 matches and the Serbian could not be in more intimidating form ahead of the US Open.
Medvedev opened as the +225 favorite at BetMGM but has seen his odds lengthen slightly despite the absence of two of his top threats. He has had a rollercoaster 2022 since falling to Nadal in the Australian Open final.
Rafael Nadal returns to the US Open for the first time in three years short of match practice and with big question marks about his fitness but few people will dismiss the Spaniard's chances of claiming a record-extending 23rd Grand Slam title.
'Serena must be prepared to live with it and say goodbye even in the face of defeat'
Indian tennis ace Sania Mirza and her Chinese partner Jie Zheng cruised into the quarter-finals of the women's doubles at Flushing Meadows.
Fifth seed Simona Halep narrowly avoided a third-round upset with a 6-1, 2-6, 6-4 win over Hungary's Timea Babos on Saturday to keep her US Open title hopes alive.
Kei Nishikori's hopes of playing at the US Open have faded further after the Japanese former world number four revealed he had tested positive for COVID-19 for a second time.
The former world number one was especially proud of the way she has managed to mould her mindset to deal with tough losses.
'I definitely think it's the time to just switch off from any future thoughts or any plans, any schedule. I've got absolutely no clue. Right now, no care in the world, I'm just loving life.'
Novak Djokovic won a record-extending sixth Paris Masters title by avenging his U.S Open final defeat against Russian Daniil Medvedev with a 4-6, 6-3, 6-3 victory in Sunday's showpiece match.
World number one Novak Djokovic had to work hard for a three-set victory over Hungarian Marton Fucsovics at the Paris Masters on Tuesday in his first match since losing the U.S. Open final in September.
A look at the 10 landmark matches from the 20-times Grand Slam champion's career.
Here are eight women to watch during the US Open which starts on Monday.
Rafael Nadal and Novak Djokovic admitted that they miss their old rival Roger Federer, who was forced to skip the US Open for the first time since 1999 due to a knee injury.
Novak Djokovic, who won Wimbledon to take his major singles titles to 21, has opted not to be vaccinated against COVID-19. He said on Thursday he could not fly to New York for the year's final Grand Slam.
Top-seeded Serena Williams said on Friday that she was not sure about the state of her balky right shoulder but felt more relaxed entering next week's US Open than last year.
Big serving Berrettini is having a breakout year, with two titles under his belt, one on grass and one on clay, and is now on the brink of becoming the first Italian male grand slam finalist in more than 40 years.
Bumrah (6/16) rattled the West Indies by picking up the first five wickets, three of which came in successive balls in the ninth over.
Images from Day 6 of the 2021 US Open in New York on Saturday.
American Rajeev Ram and Briton Joe Salisbury overcame a slow start to beat Bruno Soares and Jamie Murray 3-6, 6-2, 6-2 in the US Open men's doubles final on Friday.
A summary of Friday's action at the US Open.
Dominic Thiem has reached a Grand Slam final three times - only to lose on each occasion
Poland's third seed Agnieszka Radwanska has been bundled out of the US Open by Russia's Ekaterina Makarova in the biggest shock of the women's event at Flushing Meadows.
France's Benoit Paire has tested positive for COVID-19 and pulled out of the US Open starting on Monday, French sports daily reported on Sunday. Paire, seeded 17th at the Grand Slam event, had been scheduled to play Poland's Kamil Majchrzak in the first round at Flushing Meadows on Tuesday.
Images from Day 5 of the 2021 US Open in New York on Friday.
'It takes its toll on bigger guys. Whenever I have seen Juan maybe struggle in the heat or on TV and it looks like he's gassed out there, I can always relate'