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The Belgian has lost just once since returning in February after missing most of 2004 with a wrist injury.

Victory over the Russian in a rain-hit final means she joins Steffi Graf as the only other woman to complete an Indian Wells-Miami double.

Clijsters beat Lindsay Davenport in the Indian Wells final on 19 March.

In Miami, the 21-year-old shrugged off a rain delay of nearly an hour, then persevered as both players struggled to hold serve in a second set played in blustery winds under threatening skies.

They exchanged breaks in the fifth and sixth games before Clijsters broke Sharapova in the seventh, then held love to lead 5-3.

I think that's why I'm playing so well - I'm enjoying myself Kim Clijsters

But with Clijsters serving for the match at 5-4, Sharapova gave herself a break point with a stinging forehand winner, then fired a backhand service return winner to level the set at 5-5.

In trouble again in the next game, the 17-year-old saved two break points with unreturnable serves before Clijsters got the decisive break.

Clijsters served again for the match, squandering two match points before wrapping it up after an hour and 37 minutes.

She said: "You can wake me up now - these last four weeks in America have been incredible.

Running from corner to corner is like a piece of cake for her Sharapova on Clijsters

"I was hoping to just win two or three matches at both events to get some match rhythm. This is really hard to believe."

The victory over Sharapova means Clijsters will move back into the top 20 when the new rankings are released on Monday.

Kim can win a major this year, for sure From Lucy Have your say on tennis

"You just have to expect that she's going to get every ball back," said Sharapova.

"Running from corner to corner is like a piece of cake for her. The biggest surprise is it was her 14th straight match, and I didn't feel like she was physically fatigued.

"I'm not at the point where I can do that. She can play all day out there."

Sharapova remains at number three in the world, behind Lindsay Davenport of the US and France's Amelie Mauresmo.