Los Angeles, Mar 8 (AFP/PTI) Five-time Grand Slam tennis champion Maria Sharapova has announced that she failed a dope test at the Australian Open, and isn't sure what punishment she'll face for her "huge mistake."

The former world number one from Russia yesterday said a change in the World Anti-Doping Agency's banned list for 2016 led to an inadvertent violation, for which she will be "provisionally suspended" by the International Tennis Federation.

In a sign of what the affair could mean to Sharapova's mass of money-spinning endorsements, US sportswear maker Nike said it would halt its relationship with her as the case moves forward.

"We are saddened and surprised by the news about Maria Sharapova," Nike said in a statement.

"We have decided to suspend our relationship with Maria while the investigation continues."

Sharapova tested positive for Meldonium, a drug she said she had been taking since 2006 but was only added to the banned list this year.

"I did fail the test and I take full responsibility for it," a sombre Sharapova said at a press conference at a downtown Los Angeles hotel yesterday.

"I made a huge mistake. I let my fans down. I let my sport down that I've been playing since the age of four that I love so deeply," added Sharapova, her voice wavering.

"I know that with this, I face consequences and I don't want to end my career this way -- and I really hope I will be given another chance to play this game."

The ITF confirmed in a statement that Sharapova had tested positive on January 26 and had accepted the finding when she was notified on March 2.

"Ms Sharapova will be provisionally suspended with effect from 12 March, pending determination of the case," the ITF said.

Sharapova said she was cooperating with the ITF and did not yet know the extent of the sanctions she would face.

Her attorney, John Haggerty, said the positive test could carry a ban of up to four years, but that mitigating circumstances could see a lesser penalty.

Shamil Tarpishchev, head of the Russian tennis federation, told the TASS news agency he believed Sharapova would still have a chance to play at the Rio Olympics in August.