Roger Federer
Federer into the quarter-finals. Getty Images

Roger Federer is now just one more victory away from reclaiming the world number one ranking in men's tennis after edging past Philipp Kohlschreiber in a demanding second round contest at the Rotterdam Open.

20-time grand slam champion Federer only needs to reach the semi-final stage of this week's competition and took a commanding step towards that goal after breezing past Ruben Bemelmans in his opening round match on Wednesday [14 February].

The Swiss is now just one step away, after beating world number 36 Kohlschreiber 7-6 (8-6) 7-5 in front of a capacity crowd in Rotterdam to book his place in the quarter-final.

It took just over 20 minutes for Federer to wrap up the opening set against Bemelmans but it was clear from the start of play on Thursday evening that Kohlschreiber would offer sterner resistance, matching the Swiss game for game with the 36-year-old not as clean and clinical as he was the previous night.

Federer passed up the opportunity to take set point late on when he over hit a relatively straight forward forehand, giving Kohlschreiber the opportunity to cling on with Federer only able to find the net on the next point, forcing the tie break.

Calm and collected the previous night, Federer looked somewhat edgy in his second round match and was caught flat footed by a stunning early return to fall behind. Falling two points behind after smashing a wayward return well clear of the baseline, Federer was forced to survive two set points himself before responding with a fierce ace. It provided the late spark he needed to clinch the tie break and wrap up the opening set after 54 minutes.

Federer almost found the break he had searched so desperately for in the third game of the third set but again Kohlschreiber stood firm, fending off three break points to frustrate the Swiss. After that brief opening, the pattern of the first set resumed with each man holding serve with Kohlschreiber producing one of the moments of the contest in the fifth game, deceiving Federer with an audacious no-look drop shot.

But after standing firm for over an hour and a half, Kohlschreiber was finally broken in the 11th game, allowing Federer to serve out for a place in the final eight.

Federer is looking to move back to the summit of men's tennis for the first time more than five years after taking a wild card into this week's competition in Netherlands.

The Swiss trails current number one Rafael Nadal by 155 ATP points but with the Spaniard currently recovering from a hip injury that ended his Australian Open campaign at the quarter-final stage, he can clinch top spot again for the first time since October 2012 simply by reaching the semi-finals in Rotterdam.

Should Federer take back top spot, he will extend his record for most weeks at the top of the rankings, which currently stands at 302, while he will also replace Andre Agassi as the world's oldest world No.1, a record the American held when he was 33.