Kei Nishikori, Philipp Kohlschreiber book semi-final places in Halle

The world number 12 is looking for his third title win of the season at the ATP grass-court event in Halle, but will face the daunting task of meeting Federer to keep his dream alive.

Nishikori controlled the opening set against Steve Johnson with two breaks of serve and eventually prevailed 6-1 7-6 (7-4) after weathering a fightback from the American.

Federer did not even take to court to book his place in the last four as opponent Yen-Hsun Lu withdrew from the tournament with a back injury.

The second semi-final will see 2011 champion Philipp Kohlschreiber meet Alejandro Falla.

Kohlschreiber was given a tough work-out by Dustin Brown with the final set in his 6-4 5-7 7-6 (18-16) win taking an hour to complete.

Brown, who knocked out Rafael Nadal on Thursday, did everything he could to cause another upset, but Kohlschreiber had just too much for him.

Momentum passed back and forth throughout the match and Brown eventually levelled in the second set having led 5-0, but his luck ran out in an enthralling final set tie-break with both men wasting numerous match points before Kohlschreiber converted his seventh.

Falla had fewer problems against Peter Gojowczyk and was able to seal his progression after coming out on top in two tie-breaks, the Colombian recording a 7-6 (7-4) 7-6 (7-2) win.