World number one Roger Federer [Images] was forced to dig deep to keep his perfect record in Masters Cup round robin matches intact with a 4-6, 7-6, 6-4 win over a fired-up Andy Roddick [Images] on Tuesday.

American Roddick hassled and hustled Federer out of his comfort zone to win the first set and then had three match points in a thrilling tiebreak in the second, which the Swiss came back from 4-1 down to win 10-8.

The Wimbledon, Australian and US Open champion put himself in the driving seat to qualify for the semi-finals at the year-ending championship with his second Red Group victory when he sent an ace down the centre of the court after just under two and a half hours.

Federer won the Masters Cup in 2003 and 2004, was losing finalist last year and has still not lost in 14 group matches at the tournament.

Roddick, who drops to 1-1 for the tournament, has now lost to Federer in eight successive matches -- including the US Open final -- and won just one of 13 career matches against the dominant player in men's tennis this year.

"I put myself in a position to win tonight, it's tough right now ... I felt like I was unlucky not to win that one," Roddick said.

The 24-year-old American strode on to the court with a transparent sense of purpose and was soon dashing to the net behind his big serves in an attempt to unsettle Federer's cool.

Sometimes it worked and sometimes it just opened Roddick up to the nine-time Grand Slam winner's deadly accurate passing shots, which were particularly devastating from the backhand.

The American, watched by his new coach Jimmy Connors, succeeded enough to grab the first break of the match in game three when Federer failed in a hawk-eye appeal against a second serve called wide.

He had more break points in game five and served up four straight bombs to save his own serve in the next game, winning the set after saving another break point in game 10.

Roddick was forced to save three set points at 5-4 down in the second set but grabbed three of his own in the tiebreak, which Federer saved before levelling the match when the American charged the net only to fluff his volley.

Another backhand winner gave Federer a break early in the third set and, after Roddick lost despite forcing three deuces in the next game, the Swiss held serve with some ease and converted his second match point.

Croatia's Ivan Ljubicic takes on Argentina's defending champion David Nalbandian in the other Red Group match later on Tuesday.

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