Serena Williams breezed into the semi-finals of the US Open on Wednesday night with an emphatic straight-sets victory over Ana Ivanovic at Flushing Meadows.

The American, who sent an ominous warning to her rivals on Monday with a 'double bagel' win over Andrea Hlavackova, hardly gave the 12th-seeded Serbian a look-in on Arthur Ashe Stadium as she powered to a 6-1 6-3 triumph in just 58 minutes.

The fourth seed will face Italy's Sara Errani in the last four, the 10th seed having earlier continued her remarkable season by beating best friend and doubles partner Roberta Vinci 6-2 6-4.

Williams, 30, is the favourite to win a fourth US Open crown after her stellar summer that brought victory at Wimbledon and two Olympic gold medals.

And she wasted no time in asserting her authority over former world number one Ivanovic, racing into a 3-0 lead before the 24-year-old got a game on the board.

That came courtesy only of a fortuitous half-volley, but proved only temporary respite as 14-time grand slam singles winner Williams cruised through the remainder of the set - clinching it in just 25 minutes.

An early break for Williams in the second set saw the match continue in the same vein as Ivanovic, contesting her first major quarter-final since her 2008 French Open triumph, struggled to contain the three-time former champion.

Another break swiftly followed as Williams, runner-up to Australia's Sam Stosur at last year's tournament, completed another impressive win.

By winning the first three games, Williams made it 23 straight games in the tournament, but she still believes there is plenty more to come.

The fourth seed said: "I felt much better moving. I was excited I'm moving faster. It feels good. I felt solid.

"I felt like in the second set I could have stayed focused a little more, but she played a little better also. That's when it's really important to get refocused.

"I feel like I'm going to get more focused and serious and start playing Serena tennis in the next couple of rounds, if I get to play two rounds. That's my goal.

"I didn't think I came into this tournament playing my best, but I definitely played better in the last two matches."

Before her match, Williams had watched the final chapter in the career of her countryman and great friend Andy Roddick, who bowed out after losing to Juan Martin Del Potro.

She added: "It's the end of a great player, a legendary player. I definitely was upstairs thinking, 'Gosh, the last time this happened was Andre Agassi. How many more of these do I have to sit through?' It was great."