World No.1 Roger Federer was forced to dig deep to avoid a first-round Olympic tennis tournament exit Saturday after stiff resistance from Colombia's Alejandro Falla.

Swiss player Federer took the first set with ease but world No. 51 Falla fought back in the second and held serve to 3-3 in the decider before Federer moved up a gear to seal a 6-3, 5-7,6-3 win.

In the second round Federer will face French world No. 32 Julien Benneteau, who beat Russian No. 1 Mikhail Youzhny 7-5, 6-3.

Elsewhere, Spanish world No. 12 Nicolas Almagro qualified with a 6-4, 7-6 win over Serbia's Viktor Troicki.

Serbian No. 2 Janko Tipsarevic eliminated Argentinian player David Nalbandian 6-3, 6-4, while Steve Darcis of Belgium upset former Wimbledon finalist Tomas Berdych 6-4, 6-4.

Slovakia’s Lukas Lacko made a name for himself at Wimbledon last month by beating Rafael Nadal, but was less fortunate in the first round of the Olympic tournament, losing 7-6, 6-1 to Germany’s Philipp Petzschner, who entered the draw as an alternate after Ivo Karlovic withdrew.