DOHA, Nov 1 (Reuters) - Serena Williams underlined her dominance at the top of women's tennis on Sunday, completing her year in style with a 6-2 7-6 defeat of sister Venus in the final of the WTA Championships.

The two Americans, facing each other across the net for the 22nd time in their glittering careers, provided 84 minutes of power tennis under the Khalifa Stadium floodlights but there only ever looked like being one winner.

Serena, who came to Doha ranked second in the world behind Dinara Safina but will return home as the rightful number one, broke serve twice in a one-sided first set.

Venus did make a match of it in the second set as neither sister carved out a break point chance. Serena opened up acomfortable lead in the tiebreak, however, and sealed the title with a flashing forehand winner.