Americans Bob and Mike Bryan beat Max Mirnyi and Andy Ram 7-6, 6-3 on Sunday to win the doubles title at the ATP World Tour Finals and regain the end-of-season number one ranking.

The US duo were pushed all the way in the first set by the Belarus-Israeli pairing, taking it on a tie-break, before sealing the win with a solitary break in the second.

Victory took the Bryan brothers ahead of Daniel Nestor and Nenad Zimonjic in the doubles standings.

"It means so much," Bob Bryan said at a news conference.

"It's pretty much what we play for now... The ultimate goal is to finish number one."

Nikolay Davydenko beat weary Argentine Juan Martin del Potro 6-3, 6-4 to claim the singles title.

The wiry Russian, who has climbed to sixth in the world this week, produced a faultless display to claim the biggest title of his career and a $1.5 million cheque.