Haas is hoping to qualify for the Masters Cup

The 29-year-old beat Serbia's Janko Tipsarevic 6-3 6-7 (5-7) 6-3.

Haas currently holds the eighth and last qualifying position in the race for the Masters Cup and added 15 more points to his tally with Tuesday's win.

In the third round he faces Mikhail Youzhny, who came from a set down to beat seventh placed Fernando Gonzalez.

Victory would have guaranteed Gonzalez's place in the Masters Cup, but he remains in a strong position despite the 3-6 6-3 6-3 defeat.

Gonzalez will only miss out if two of the chasing pack reach the final in Paris.

"I really like this tournament but I've never won a match here," Gonzalez said. "That's the sixth year in a row."

Tommy Robredo is also still in the hunt after battling past Gilles Simon. Robredo took the first set but Simon took it to a decider and put the Spaniard under intense pressure before succumbing 6-4 2-6 6-4.

Robredo lies a point behind Haas in ninth place and next faces Guillermo Canas, who beat Andreas Seppi 6-3 7-6 (7-5) and still has an outside chance himself.

Tomas Berdych, who came into Paris in 12th in the race, kept his hopes alive with a 6-3 6-3 win over Mario Ancic.

But Haas's win means anyone hoping to overtake him in the race, including Britain's Andy Murray who was in 11th, must reach at least the quarter-finals.

Haas, who pulled out of Lyon last week with a stomach problem, is troubled by his right shoulder and his rivals may take encouragement from his ailments.

"It's now been six weeks on the road," Haas said. "I was ill last week. I have had so many injuries. I will try my best here, but I don't want to put pressure on myself.

"I'm looking forward to the end of the season."