Serena Williams set up a titanic Wimbledon fourth round showdown with sister Venus as the world number one staged a dramatic final set fightback to beat Britain's Heather Watson 6-2, 4-6, 7-5 on Friday.

Williams, bidding for a sixth Wimbledon title and a calendar Grand Slam, was on the brink of a humiliating third round exit when Watson served for the match at 5-4 in the final set.

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But Serena, who had trailed 3-0 in the decider, showed why she has won 20 Grand Slam titles as she broke back before finally sealing an epic escape in two hours and 14 minutes in front of an enthralled Centre Court.

The 33-year-old American will face Venus on Monday for the first time in a Grand Slam since beating her in the 2009 Wimbledon final.

The sisters' last meeting came in 2014 when Venus won in Montreal, but Serena holds a 14-11 advantage over the 35-year-old in their career head to head.