Good afternoon and welcome to live updates of the opening singles match of the 2017 Nitto ATP World Tour finals. It's world No.2, Roger Federer against American Jack Sock in Boris Becker group.

GAME, SET AND MATCH! - FEDERER 6-4 7-6 SOCK. Federer's bid for a seventh end of season title is off to a solid start following a hard-fought straight sets victory over Jack Sock at the O2. The Swiss takes the TB 7-4 and completes the victory in one hour and 31 minutes.

TB UPDATE: Sock rallies for 4-4 but then double faults. It's 5-4 to Federer with two serves for the Swiss to come...

TB UPDATE: It's 4-2 to Federer at the change of ends. Big ask for Sock now.

TIE BREAK! - FEDERER 6-4 6-6 SOCK. Tie break time! Federer has been completely untroubled on serve throughout and he eases to a love hold. Pressure? What pressure?

FEDERER 6-4 5-6 SOCK. An 11th ace and a crunching crosscourt forehand winner earn Sock the minimum of a tie break after he was once again pushed the distance on serve. Federer's frustration will be growing on the back of another missed opportunity on BP and he must now hold firm to take us to the TB.

FEDERER 6-4 5-5 SOCK. Far too good. Federer surges to a love hold. No problem for the Swiss who hasn't faced a BP yet.

FEDERER 6-4 4-5 SOCK. How many get out jail free cards does Sock have left up his sleeve? The world No.9 makes a succession of unforced errors to give Federer another chance to break from deuce. The Swiss misses with a backhand down the line and then slaps another chance into the net off the same wing. Sock is put through the grinder but survives with big serving to stay alive.

FEDERER 6-4 4-4 SOCK. Roger shrugs off his disappointment with a love hold. Sock went for broke at 40-0 but bulldozed a ferocious forehand just long of the baseline.

FEDERER 6-4 3-4 SOCK. That's a big, big hold from Sock. Federer looks all set to strike a decisive blow at 15-30, but the American refuses to relinquish his serve, forcing it to deuce before keeping his nose in front with a brutal wide ace to finish.

FEDERER 6-4 3-3 SOCK. Once more Federer responds in kind. A slick serve and volley followed by a wrong-footing forehand winner snare the love hold. All square. Who will blink first?

FEDERER 6-4 2-3 SOCK. And there isn't one! Sock's service rhythm is right in the zone as he mixes it up nicely to keep Fed guessing. It's a love hold once again.

FEDERER 6-4 2-2 SOCK. Whatever you can do... Federer rushes through his own hold to 15 to move level. You sense the Swiss is waiting for his moment to pounce here. Sock can't afford any lull now.

FEDERER 6-4 1-2 SOCK. It's a purple patch for Sock. He marauds through another easy hold for the loss of one point. It's impressive stuff. His confidence is clearly on the up as he maintains the scoreboard advantage in Set 2.

FEDERER 6-4 1-1 SOCK. Federer wastes little time with the riposte. This has been a highly competitive match with the occasional sprinkle of truly entertaining moments - but can Sock actually do any damage to the Fed defence to put the final result into real doubt?

FEDERER 6-4 0-1 SOCK. What a contrast between opening service games! That's much better from Sock as he starts Set 2 with a stylish love hold. A drop volley and a well retrieved crosscourt forehand on the scamper do the damage as he gives his own belief a much-needed injection.

SET! - FEDERER 6-4 SOCK. A pair of aces clinch the game to 15 and sees Federer take the opener in just 36 minutes.

FEDERER 5-4 SOCK. It's a love hold for Sock, who hammers down some big serving to breeze through the hold in double-quick time. Over to Roger now to try and serve it out.