Reigning US Open champion Serena Williams insists she is not feeling any additional pressure as she attempts to complete a calendar Grand Slam.

World number one Williams heads to Flushing Meadows next week having already claimed the Australian Open, French Open and Wimbledon in 2015.

Only three women have swept all four majors in a single season - Maureen Connolly Brinker, Margaret Court and Steffi Graf.

Graf was the last female to achieve the feat in 1988.

Williams - 48-2 on the WTA Tour this season - is seven wins away from adding her name to that illustrious list but the 21-time grand slam winner is treating her 2015 US Open campaign like any other.

"I don't feel that fresh pressure. If I make it far then maybe I will but, as of now, I really don't feel any. I'm just here to perform and to do the best I can," said Williams, who will face Vitalia Diatchenko in the first round in New York.

"I always feel there's another record, then there's always another person to catch up with or to pass. I never really thought I would be in this position where I would even be talking about records, passing Steffi Graf or even mentioning Margaret Court.

"I just grew up trying to be the best I could and do the best I could. I worked really hard for everything so to even be mentioned in that conversation is great."

Williams added: "Wimbledon gave me unbelievable practice for this.

"At Wimbledon I was going for the second Serena Slam [holding all four grand slam titles at the same time]. That is rare. So that really gave me the best practice and preparation in terms of going for the Grand Slam."