The French pairing of Tatiana Golovin and Jerome Haehnel only gained a berth in the event when Germany was forced to withdraw, but they were too good for the fourth-seeded American team of Ashley Harkleroad and Mardy Fish, winning 2-1.
Golovin gave the French the lead with a three-set win over Harkleroad, before Haehnel secured the tie with an upset win over Fish, also in three sets.
With the result decided and midnight looming, the French elected to forfeit the mixed doubles, an ankle injury to Golovin the official reason.
The women's singles match went the way the rankings indicated, with Golovin prevailing 6-3, 4-6, 6-2 in an error-riddled match punctuated by regular service breaks.
Both players looked rusty in their first outing of the season and the match produced 75 unforced errors, but Golovin was able to compose herself in the third set.
The exciting teenager, ranked 22nd in the world despite ankle problems earlier this year, admitted she was a bit sluggish after a late arrival in Perth.
The men's singles was not one for the archives either. There were a staggering 92 unforced errors, with Haehnel admitting it wasn't a great match after winning 7-5, 4-6, 7-6 (7-3).
Haehnel, who avoids plane travel and whose main claim to fame is a French Open win over Andre Agassi, is ranked 166 places below Fish at 213.
Having upset the Americans in their first tie of the round robin group matches, France is in a good position to qualify for Friday's final.
Earlier, host nation Australia also caused a massive upset, beating tournament favourite Russia in their Group A tie.
The Russian pairing of Nadia Petrova and Dmitry Tursunov are top seeds, but lost 2-1 to the Australian pairing of Alicia Molik and Mark Philippoussis.
Both Molik and Philippoussis are on the comeback trail, the latter after a major form slump and Molik after a serious illness that threatened her career.
Although both Australians have been in the top 10 during their careers, they find themselves ranked in triple figures entering 2007.
Molik, ranked 164th after a middle-ear infection that sidelined her for almost two years, upset the sixth-ranked Petrova in three sets, 6-2, 2-6, 6-2.
Philippoussis, ranked 114th, then completed an unlikely win with a straight sets victory over world No 22 Dmitry Tursunov, 6-4, 7-6 (7-0).
The Russians gained some consolation with a 7-6 (8-6), 6-1 win in the dead mixed doubles rubber.—AFP