Serena Williams battles on as US Open farewell underway

The 23-time Grand Slam winner -- who earlier this month signalled she plans to retire from tennis after the tournament -- drew on all of her experience to down lowly ranked Montenegrin opponent Danka Kovinic 6-3, 6-3.

A galaxy of celebrities ranging from Hollywood stars, fashion icons and former presidents were out in force at Flushing Meadows' Arthur Ashe Stadium to watch could have been Williams final appearance in a Grand Slam singles match.

But the 40-year-old ensured that her legions of fans will have at least one more chance to savor her talents as she dug out victory despite an error-strewn display.

"I feel so comfortable on this court and in front of everyone here," a jubilant Williams said after her victory.

"The crowd was crazy – they really helped pull me through. I was really pumped," added Williams, who won the first of her Grand Slam titles in the same arena in 1999 as a 17-year-old prodigy.

Williams admitted that deciding to walk away from the sport after 27 years as a professional was "such a hard decision."

"I think when you are passionate about something it is always hard to walk away," she said. "I have been trying to decide what to do. I love this game.

"But I was just like 'Alright, I think now's the time'. I have a family, there's other chapters in life. I call it evolution."

A sell-out crowd of 23,500 had roared its appreciation for Williams as she strode into the arena wearing a striking sparkling bodice and black skirt comprised of six layers -- one for every US Open title she has won.

The roll-call of A-listers on hand for the occasion included former US President Bill Clinton, Vogue editor Anna Wintour, former heavyweight champion Mike Tyson, tennis legend and Hollywood stars such as Hugh Jackman and Queen Latifah.

In an interview with NBC's Today show on Friday, Williams declined to confirm that she would retire in New York -- and would not even rule out playing into 2023.

"I think so, but who knows?" she told NBC when asked if she would retire.

But in a post on Instagram on Monday just hours ahead of her first round clash, Williams again signalled the end was nigh.

"Thank you everyone," she wrote. "It's been incredible."

ALSO READ: Rugby World Cup boss suspended by French sports minister

- Tsitsipas stunned -

In other women's draw action on Monday, former world number one Simona Halep, seeded seventh, was the biggest casualty in the first round, crashing out 6-2, 0-6, 6-4 to Ukrainian qualifier Daria Snigur.

But there were no such problems for US teenager and 12th seed Coco Gauff, who cruised past France's Leolia Jeanjean 6-2, 6-3.

Meanwhile the men's draw got under way with a stunning upset for Greek fourth seed Stefanos Tsitsipas, who was bundled out by Colombian qualifier Daniel Elahi Galan 6-0, 6-1, 3-6, 7-5.

Earlier, Russia's defending champion Daniil Medvedev routed Stefan Koslov of the United States in the top half of the draw.

The Russian comfortably dispatched world No.111 Kozlov 6-2, 6-4, 6-0 in 2hrs 1min.

Medvedev, bidding to become the first man to defend the US crown since Roger Federer retained the title in 2008, faces France's Arthur Rinderknech in the second round.

Britain's Andy Murray, another veteran well into the twilight of his career, marked the 10th anniversary of his maiden Grand Slam win with a straight sets defeat of Argentinian 24th seed Francisco Cerundolo.

The 35-year-old Scot showed no signs of recent cramping problems in a 7-5, 6-3, 6-3 win, but admitted afterwards: "It felt like five sets."

It was Murray's first straight sets win at a Grand Slam event since 2017.

Elsewhere Monday, Wu Yibing claimed a piece of history in the men's draw, becoming the first man from China to win a Grand Slam singles match since 1959.

The qualifier upset Georgia's 31st seed Nikoloz Basilashvili 6-3, 6-4, 6-0.

But there was agony for China's other player in the men's draw, Zhang Zhizhen who squandered seven match points in a 3-6, 6-7 (4/7), 7-6 (11/9), 6-1, 6-4 defeat to Tim Van Rijthoven of the Netherlands.

Spain's Rafael Nadal, chasing a fifth US Open crown and 23rd Grand Slam title overall, begins his campaign on Tuesday against Australia's Rinky Hijikata.