Second seed Serena had to rescue a match point before she overcame fourth seed Elena Dementieva in three sets.

Dementieva took the first set 7-6 after winning the tiebreak 7-4. Serena levelled the match after taking the second set 7-5.

In the decider the Dementieva missed a match point, when a slight netcord helped a Williams volley into play.

The American then broke to 7-6 and held serve to book her place in her fifth final.

Current champion, Venus Williams, overcame number one seed Dinara Safina comfortably in straight sets 6-1 6-0 to reach her eighth final.

Venus is chasing her 3rd consecutive womans singles title and her fourth in five years.

This will be the fourth time the sisters meet at this stage of Wimbledon. Serena has won two out of the three encounters.