Doha: Roger Federer will play Jo-Wilfried Tsonga in the semi-finals of the Qatar Open after both won their last-eight matches in the Qatari capital.

Tsonga enjoyed an untroubled 6-2, 6-1 win over Spanish left-hander Albert Ramos before Federer dropped a set on his way to a 6-3, 5-7, 6-4 win — his 20th straight triumph — over Italian Andreas Seppi.

"It's difficult to play against him [Federer]," the Frenchman said. "I have to be perfect and play my best tennis but I know I can do it." Tsonga started strongly against Ramos, breaking the 23-year-old in the opening game. The world No.6 broke at the third attempt following a Ramos error.

Tsonga then held to serve to love in his first two service games, taking a 3-1 lead.

Ramos, ranked a career-high 66th in the world, seemed to overcome his early service loss, but Tsonga then upped the tempo, hitting a series of bruising ground strokes the Spaniard could only parry. Tsonga blew the first of three set points, but won it at the second attempt with a blistering serve.

With the first set in the bag, Tsonga was more expansive, advancing to the net to hit a range of volley and smash winners.

Tsonga survived a scare in one game, saving three break points and then wrapped up the match swiftly as Ramos faded.