Serena Williams looked every inch the title favourite as she powered past Francesca Schiavone in the first round of the US Open.

The pair opened the night session on Arthur Ashe, with top seed Williams beginning the defence of the trophy she won for a fourth time 12 months ago.

The 31-year-old has won eight titles already this season, including the French Open, and former Roland Garros champion Schiavone simply had no answer.

She won just six points in the first set as Williams sent the ball flying to all corners of the court with immense power and precision.

For a long time it looked like Schiavone would not win a single game as Williams made it 10 games in a row.

She had a point for an eleventh, which would have left her serving for the match, but this time Schiavone held off her opponent and finally got on the board with a forehand volley.

But that was as good as it got for the Italian as Williams wrapped up a 6-0 6-1 victory after exactly an hour when Schiavone put a forehand long.

Next up for Williams is Kazakhstan's Galina Voskoboeva.

Venus Williams also impressed as she rolled back the years to beat Belgium's Kirsten Flipkens.

Roared on by an energetic New York crowd Williams showed no signs of the back problems that have sidelined her for most of the year as she demolished her younger opponent 6-1 6-2.

The 33-year-old American, the second oldest player in the women's singles draw, provided a glimpse of the form that saw her win the U.S. Open in 2000 and 2001 as she romped to victory in just one hour and 24 minutes.

"It's good to be back. I was glad to close it out today," said Williams.

Williams has only played 18 matches this year and slipped to 60th place in the world rankings, while Flipkens is enjoying the best season of her career.

The 27-year-old made the semi-finals at Wimbledon in July, her best result at any grand slam, and was seeded 12th for the US Open. Earlier this month, she beat Williams in Toronto after losing the first set 6-0.

Flipkens was the first notable casualty in a wide open women's draw that promises to be one of the most competitive years.

China's Li Na, the 2011 French Open champion and runner-up in Australia this year, needed just 64 minutes to crush Olga Govortsova of Belarus 6-2 6-2.

And Poland's Agnieszka Radwanska, the third seed, was even more ruthless, thumping Spain's Silvia Soler-Espinosa 6-1 6-2 in 63 minutes in the opening match on the center court.

Ninth seed Jelena Jankovic has quietly been showing very good form this year and she overcame a potentially tricky hurdle in rising American star Madison Keys.

The 18-year-old reached the third round of Wimbledon but has been troubled by a shoulder injury and went down 6-3 6-4.

Eighth seed Angelique Kerber had to wait until late in the day to get on court against Lucie Hradecka and wasted no time getting off it again after a 6-1 6-1 victory.

No result was more welcome, meanwhile, than Alisa Kleybanova's 6-4 3-6 7-5 victory over Monica Puig.

This is the Russian's first grand slam appearance for two and a half years, during which time she has overcome Hodgkin's lymphoma.