Hurricane Isaac was forecast but Cyclone Serena arrived instead and threatens to blow Victoria Azarenka away in the women's US Open final on Saturday night (10am Sunday AEST).

Sweeping unrelentingly towards a 15th grand slam crown, Serena Williams ensured a showdown between women's tennis's two most dominant forces with a 6-1 6-2 semi-final swamping of Italian Sara Errani.

The top-ranked Azarenka won the semi-final battle of the scream queens 3-6 6-2 6-4 against French Open champion Maria Sharapova and then dubbed Williams the elephant in the room that she must block out to have any hope of taking home the trophy.

Showing no mercy to her rivals, the American juggernaut has conceded only 19 games in six rounds and never dropped while blasting a tournament-best 50 aces en route to her sixth final in New York.

Oh, and she will carry a 9-1 winning record over Azarenka into the title match.

"She's definitely the toughest opponent there is in the draw and being in the final makes it even more difficult," Azarenka said. "So it's definitely going be a tough one.

"Our record, it says it all. I mean, I haven't won in any last meetings, so I definitely need to find something to surprise her because she's in a great form, feeling really confident right now.

"She has everything on her side."

In their most recent encounter, at the Olympics last month, Williams thumped Azarenka for the loss of just three games and the Belarusian knows she must be big and brave to spring a boilover.

"When I go to play against her, I don't think that I'm playing against Serena. I just try to go the same way and try to focus more on myself," the top seed said.

"But you definitely know that it's going to be a big adversity there on the court against you.

"You have to be prepared to make sure you want to dig deep and accept the challenge.

"I have to try to return well, definitely, and serve because with Serena it's not really the long rallies.

"It's all about who grabs the first opportunity, who is more brave to step it up right from the beginning."

Williams can join older sister Venus and the great Steffi Graf as the only women to claim the Wimbledon-Olympic-US Open treble in the same season.

"It will probably be the best summer I've ever had," the 30-year-old said.

"If you win the Olympics and Wimbledon and this, it would be kind of cool. So, yeah, it will be awesome."

Williams snared her maiden major in New York at 17 in 1999 and raised the trophy again in 2002 and 2008 before being trumped by in last year's decider by Samantha Stosur.

"I definitely want to hold that trophy and to lift it up," the fourth seed said.

"Last year was different. I didn't get to bed until after 4am (the night before). I had to come right back and play again. Went fast.

"This year, I know it sounds weird, but I have more experience than I did last year.

"But I don't have anything to lose. I feel like I'm going up against - I personally think - the most consistent and the best player this year, being Victoria Azarenka."

After once again succumbing to Azarenka in a sequel to their Australian Open final, Sharapova said an upset shouldn't be dismissed.

"She's No.1 in the world," Sharapova said. "There's no reason why she shouldn't have a chance."