LONDON (Reuters) - Serena Williams roared into a her seventh Wimbledon singles final with a 6-3 7-6 victory over Victoria Azarenka on Thursday.

The 30-year-old American, contesting a 21st grand slam semi-final, was unstoppable in the opening set as Belarus's Azarenka barely got a sniff of a chance.

However, the second set was a much tighter affair as Azarenka clawed her way into the match, breaking the Williams serve for the first time in the sixth game.

She pushed the four-times champion into a tiebreak and saved a match point when Williams lobbed long but gave her opponent another chance and the American took it with her 24th ace.

She will face Poland's Agnieszka Radwanska in Saturday's final.

(Reporting by Martyn Herman, editing by Pritha Sarkar)