The United States sill face Spain tomorrow for a place in the Hopman Cup final after overcoming a scare from France in last night's 2-1 win.
Venus Williams and John Isner once again formed a solid pairing at the Perth Arena, winning the mixed doubles 6-7 6-2 (10-8) and keeping their tournament alive.
The result looked to be going the other way earlier in the night when world No.86 Mathilde Johansson had a 4-1 lead over Williams in the second set of their encounter and was within touching distance of victory for France.
The crowd of 7936 sat stunned as the five-time Wimbledon winner committed a raft of unforced errors, dropping the first set before coming back for a 3-6 7-5 6-4 win.
Despite appearing to be hampered by an unknown injury, Williams said she was physically in good condition but needed to improve her game.
"I got a third win in the third set, I just got through the second and tried to put some good serves in, that helped a lot," she said. "I've just been working on finding my consistency, finding my feet and just trying to find my best tennis."
The United States was forced to come from behind after Jo-Wilfried Tsonga dispatched Isner 6-3 6-2 in the opening rubber.
Having previously struggled against the 206cm serving specialist, Tsonga came into the match determined to make his opponent run.
The unflappable Frenchman was aggressive but added enough deft touches at the net to scatter his opposite number and give his country the upper hand.
The performance displayed the sort of form Tsonga is hoping will carry him to a grand slam victory this year.
"It's never easy against John usually so I'm really happy with the way I played today," he said.
"It's a really good start to 2013 and I would love some more (results) like this.
"I was a bit quicker on court than before so I think it's a good sign for the rest of the competition and for Melbourne."
Isner took to the court with strapping on his right knee and racked up several uncharacteristic unforced errors in the face of Tsonga's onslaught.
The big-serving American said he was having a slight problem with tendonitis but didn't expect it to affect him for the coming season.
"Normally it takes me a while to really get going, I'm not worried about it though," he said.
"Three years ago when I first played this event I didn't play so well here but I won the next tournament so that's why I come here, to get practice matches.
"It certainly wasn't my best, I was missing a lot of shots I would liked to have made.
"I'm not freaking out about it"
The second-seed USA will now meet fourth-seed Spain for a spot in the final, with both group B teams having won two ties each.
Tosnga's next opponent will be South African surprise packet Kevin Anderson, who has taken the scalps of Isner and Spain's Fernando Verdasco already at the tournament.
He said Anderson had steadily been improving to the point he could beat the world's best and was expecting a tough match when the pair meet on Friday.
More than 40,000 people have attended the event so far, leaving organisers well on track to surpass last year's total attendance of 72,776.