Tomas Berdych of the Czech Republic celebrates winning his men's singles tennis match against David Ferrer of Spain at the ATP World Tour Finals at the O2 Arena in London, Nov 6, 2013. [Photo/Agencies]

LONDON - Rafael Nadal sealed the year-end No 1 ranking for the third time by edging Stanislas Wawrinka 7-6 (5), 7-6 (6) at the ATP World Tour Finals on Wednesday.

Nadal also qualified for the semifinals of the event with two straight wins in Group A. He had crushed fellow Spaniard Ferrer in straight sets.

Tomas Berdych kept his hope of qualifying alive by upsetting third seed David Ferrer.

Berdych, the fifth seed and losing to Wawrinka in his first match, cruised to a 6-4, 6-4 win over Ferrer.

Nadal, the 13-time Grand Slam winner, can't be surpassed by No 2 Novak Djokovic in the world rankings with two victories.

Nadal, who won 10 titles this season, also ended the season as world No 1 in 2008 and 2010.

"A lot of emotions today, it's the perfect scenario to finally be the year-end number one," Nadal said.

"Being number one at end of the season is something really difficult as there are some unbelievable competitors out there."

Berdych must now defeat Nadal, who has already secured his spot in the semifinals, in his final group match on Friday. Ferrer, who was beaten by Djokovic in the final of Paris Masters, is almost certain to be eliminated.

"It was not easy at all, you can see David is a great player," Berdych said. "I'm happy with the way I played today."