Maria Sharapova has downplayed her chances of winning a second US Open crown this year after returning from shoulder surgery but believes she can go on to regain the world number one spot.

"With every tournament I feel physically I'm getting better and getting a good sense of the court but it's still a work in progress," the three-times Grand Slam winner said ahead of the final major of the season which begins on Monday.

"I'd like to forget I was gone for a long time but you have to put things in perspective."

The 22-year-old Russian, who only returned to singles action in May after a nine-month layoff, said while she would certainly give the US Open her best shot and is "absolutely" sure of climbing back to the tennis summit.

"I'm a competitor and have played many tournaments and won quite a few," said Sharapova, who first claimed the world number one spot in 2005.

"You want to be the winner and if someone tells you otherwise they wouldn't be telling the truth."

While the Russian has not won any titles since her comeback, she has beaten world number seven Vera Zvonareva, eighth-ranked Victoria Azarenka and number 13 Nadia Petrova and seems to be improving every week.

The Russian reached the LA Championships semi-finals and on Sunday lost the Toronto Cup final to compatriot and world number four Elena Dementieva 6-4, 6-3.

"I think it was a really great week for me," Sharapova said. "Playing six matches was great leading up to the US Open."

Sharapova fondly recalled her title run at the 2006 US Open, where she beat Belgium's Justine Henin in the final.

"Winning my second major took quite a bit of time," said the 22-year-old, who won her first aged 17 at Wimbledon in 2004.

"Justine was playing really well but my game had been building and it was one of those matches where I came in without a big game plan because I felt like if I was going for my shots I had a chance," she said in an interview arranged by WTA sponsors Sony Ericsson.

Last October, Sharapova had her shoulder operation and did not return to singles competition until May in Warsaw.

Her record is 22-7 since her return, pushing her world ranking up to 30th and guaranteeing a seeding at the US Open.

During her seventh months of rehab, Sharapova, whose last Grand Slam title was the 2008 Australian Open, thought back to her great wins, which aided her recovery.

"I go back to the tough days when I wasn't feeling great or wasn't thinking straight and still managed to pull it together," she said. "I think about how I was able to turn it around."

While her ground attack and return game is sharp, Sharapova is not consistently hitting her serves at pre-surgery speeds due to a new, abbreviated motion and is frequently double faulting.

While the Russian knows she must improve that aspect of her game to beat the tour's best, Sharapova also said she must get used to playing long matches again to get back to the top.

"I can do all the running or Pilates I want, work myself until I'm blue in the face but when you go on court for the first time after months on end your body isn't used to the whole thing," she said, hinting the US Open may have come too soon.