Russia's Maria Sharapova has pulled out of the $US1.5 million ($A1.62 million) Dubai Championships citing a viral illness.

The Australian Open champion, who also won in Doha last week, is unbeaten in 2008 and had been scheduled to play her first match in Dubai on centre court in Tuesday's evening session.

"Unfortunately I have been battling a virus for several days and it's reached a point where I'm unable to compete," the world number five said in a statement.

Maria Sharapova claimed her second title of the year and the 18th of her career when she defeated unseeded Vera Zvonareva 6-1 2-6 6-0 in an all-Russian final at the Qatar Open on Sunday.

Playing in a packed 5,000-seat stadium, fourth seed Sharapova made a dreadful start, dropping the opening game to love.

But she repaired the situation immediately, levelling at 1-1 and then overwhelming her opponent with her deep groundstrokes and powerful forehand.

Fourth seed Maria Sharapova extended her unbeaten run to 13 matches with victory over Poland's Agnieszka Radwanska in the Qatar Open semis.
The Australian Open champion controlled proceedings as she came through 6-4 6-3 to set up a final against her fellow Russian Vera Zvonareva.

"It was a good opportunity for me to go out and play against a player who had beaten me," Sharapova said. "I think she did a good job early in the match, but I was able to get ahead and play good tennis."

Sharapova had two breaks to Radwanska's one in the first set, and broke the Pole three times in the second set.

Australian Open champion Maria Sharapova maintained her unbeaten record in 2008 as she powered her way into the semifinals of the Qatar Open with a victory in less than an hour.

The fourth seed brushed aside 17-year-old Danish prospect Caroline Wozniacki 6-1 6-0, her 12th successive victory in all competitions.

"It was a pretty solid performance apart from one game in the second set," said Sharapova. "I felt pretty comfortable from the beginning. I was aggressive. I served and returned pretty well and felt good."

A resurgent Maria Sharapova maintained her perfect start to the season at the Qatar Open on Wednesday.

Seeing her first tournament action since winning the Australian Open last month, the fourth-seeded Sharapova defeated fellow Russian Galina Voskoboeva, 6-4, 4-6, 6-1, in the second round of the $2.5 million event.

Including her title at Melbourne and two Fed Cup wins in Russia's first-round tie with Israel earlier this month, Sharapova has now won all her 10 matches this season.