German number one Nicolas Kiefer stepped up his challenge in the Salem Open when he overcame Australia's Jason Stoltenberg 6-3, 6-2 to reach the quarter-finals at Victoria Park yesterday. And third seeded Kiefer said he would not be in a generous mood when he took on his doubles partner, Nicolas Lapentti, for a place in Saturday's semi-finals. Kiefer is hoping to go one better in Hong Kong after reaching the same stage last year when losing to a rejuvenated Andre Agassi. World number 18 Kiefer stayed on course for a possible semi-final showdown with Britain's Tim Henman but the 23-year-old German, who once trained with the great pole vaulter, Sergei Bubka, will have to overcome a stiff hurdle in Lapentti. Lapentti, the tournament's fifth seed, needed three sets but showed fighting qualities before disposing of American qualifier Kevin Kim 6-1, 3-6, 6-2 to also advance to the last eight. Kiefer was looking forward to a good match against Ecuadorean Lapentti. 'Against Nicolas, it's going to be a tight match. He knows my game and I know his. Nicolas is a tough player to beat and we have both been playing well. I hope to beat him,' said Kiefer moments after teaming up with Lapentti to win their first-round doubles match against Hong Kong's Melvin Tong and John Hui 6-3, 6-0. Also through were Britain's Henman, who swept aside Mariano Zabaleta of Argentina 6-2, 6-4 - his second victory in five meetings against the Argentine - and Michael Chang, who stayed on course for a fourth Salem title with a 6-1, 6-2 victory over Dutchman Sjeng Schalken. Kiefer was impressive as he won for the second time under the floodlights against the veteran Stoltenberg, who played in the first Salem Open in 1990. The German broke 62nd-ranked Stoltenberg in the first game and led 4-2 with another break of service after the Australian played a return long. He then closed out the set by holding service. The second set followed a similar pattern as Kiefer continued to press home the advantage with his powerful serve. 'I started off very well when I was up a break in the first game. But then I didn't pay attention to my shots and he started coming back. But I think I played a good match overall,' said Kiefer. Lapentti, a distant cousin of former French Open champion Andres Gomez who won in Hong Kong at the now-defunct Seiko Super Tennis tournament in the mid-eighties, is coming off a recent knee injury and was happy to get through his match without any real dramas. 'I didn't know what to expect because that was the first time I've seen him play. The way I played the first set, I thought I was in control,' said the 24-year-old Lapentti, ranked 21st in the world. 'The second set was a completely different story as he was moving a lot better and not missing many shots, but I was playing well again after I got my first break in the third. I got a bit tired but luckily I got through it.' Lapentti easily won the first set but suffered a lapse of concentration to lose the second set. But the talented Ecuadorean, who reached two semi-finals on the ATP Tour this year, and has three career singles titles, found his form again to dispatch Kim, winning the last point when he ripped a forehand down the line which Kim returned into the net. The 22-year-old Kim had played four matches - three qualifying matches and one match in the main draw - before meeting his more illustrious opponent but Lapentti said playing in the qualifiers can give a player an edge. 'Sometimes coming through from the qualifiers is good because you have a number of matches under your belt,' said the Ecuadorean, who is making his first appearance in Hong Kong. 'I injured my knee in practice and I couldn't practice for three weeks. I didn't work very hard coming here. My treatment on my knee was not 100 per cent so in the second set my level was down. But I just tried to hang in there and waited for the opportunities to break. Luckily it came,' he said. Lapentti said he wasn't feeling 100 per cent at the moment but said he will have a day off today before taking on Kiefer for a place in Saturday's semi-finals. 'I'm sure I will be ready on Friday,' said Lapentti.