Venus Williams powered her way into the semi-finals of the Dubai Duty Free Tennis Championships with a hard-fought 6-3 7-5 win over Flavia Pannetta.

The Italian had crushed second seed Agnieszka Radwanska in the third round but struggled to hold on to her serve throughout the contest as she eventually succumbed in straight sets despite a battling display in the second.

In truth Pannetta will feel as though she should have run Williams closer, having earned some 15 break points in the match, but only managing to convert on four occasions.

In contrast Williams carved out nine opportunities to break and was successful on six occasions as she booked her place in the last four, despite only entering the tournament as a wildcard.

The 33-year-old dropped her serve twice in the first set but was clinical when making the most of her own opportunities and eventually held on at a crucial time to claim the first set.

The trend continued in the second with both players continually applying pressure on their opponents serve.

Williams, who won the tournament in 2009 and 2010, would once again break Pannetta on three occasions but she rarely looked in command of the set as the 31-year-old continually threatened to claw her way back into the match.

She would twice secure breaks of her own but wasted numerous chances as Williams managed to hang on to her advantage and eventually claim victory in 1hr 38minutes.

Williams will now play eighth-seed Caroline Wozniacki of Denmark who eased to a 6-1 6-2 win over Sorana Cirstea of Romania.