Australian Open finalists Maria Sharapova and Serena Williams have both withdrawn from next week’s the Dubai Tennis Championships due to injury. No. 1 Sharapova will not play the $1.5-million event due to a hamstring injury she suffered several weeks ago in Tokyo.

“I’m very disappointed to have to withdraw,” read a statement from the Florida-based Russian. “The hamstring that I injured in Tokyo is not yet healed.

“I tried everything possible to be in condition to play, but unfortunately I’m not ready. I’m looking forward to continuing to recover as quickly as possible so that I can get back on the court competing.”

Melbourne winner Williams continued her February string of withdrawals, having not played since lifting the Grand Slam nearly three weeks ago over Sharapova 6-1, 6-2.

The American followed up her pullout from this week’s tournament in Bangalore by pulling from Dubai, citing flu. Justine Henin, Svetlana Kuznetsova and Martina Hingis head the women’s field.

Russian tennis star Maria Sharapova yesterday became the latest celebrity to be appointed a Goodwill Ambassador for the United Nations Development Program (UNDP). The tennis ace agreed to use her charisma and fame to gather support for the fight against global poverty.

She also donated $100,000 to help improve the public service sector in the parts of the Ukraine, Belarus and Russia most badly affected by the world’s worst nuclear accident, the 1986 Chernobyl disaster.

She says, “My first step is to focus on the Chernobyl-affected region, where my family has roots. Today, it is poverty and lack of opportunities that pose the greatest threat for young people in the Chernobyl region.”

Sharapova joins actor Danny Glover and soccer players Zinedine Zidane and Ronaldo, who are already working for the development fund.

Top-seeded Maria Sharapova withdrew with a left hamstring injury Saturday during her semifinal match against Ana Ivanovic at the Pan Pacific Open in Tokyo.

Sharapova sought medical assistance before opting out of the match.

Her withdrawal means the fifth-seeded Ivanovic will face No. 2 seed Martina Hingis in Sunday’s final.

Ivanovic was leading, 6-1, 0-1, when Sharapova could not continue.

“I started to feel the tightness at the Australian Open, but this was not the same pain,” said the 19-year-old Sharapova. “After six or seven matches in 14 days, you’re bound to be sore (and) the pain didn’t get any better.”

“It’s unfortunate that she had to retire,” Ivanovic said. “It’s not the way I like to end the match.”