Venus Williams has reached the fourth round of the Sony Ericsson Open in Miami, Florida, after a hard-fought victory over Aleksandra Wozniack.

The world number 65 started positively by breaking the world number 20's first service game.

Despite a break back from Williams, Wozniack was able to find her second break of the set to take it 6-4.

Neither player was able to hold serve in the second as they both struggled to get a hold of the match.

Williams eventually managed to take a fourth break from the Canadian on her way to claiming the set 6-4.

Wozniack looked sharper in the deciding set, and she was duly rewarded with a break of serve to take a 3-2 lead.

However, Williams produced a sudden surge at the same time that Wozniack began to crumble under the pressure, and the American found a service break to level things up.

This only seemed to encourage a reversal of roles as Wozniack dominated Williams on her next service game to take a 5-4 lead.

Wozniack appeared extremely nervous as she tried to serve out the match, and Williams took advantage of this by winning what was a tense game. Both players then held serve to take the match into a tie break.

Williams held her nerve in the tie break as she found four mini breaks to win 7-5.