In the outright battle, Jani - who also had pole position last year - says he has more speed if his rivals get close in second qualifying on Thursday night.
"There is some left. I hit a lot of traffic. I did lose quite a bit of lap time. We know we have quite a bit left in our pockets, if we need it tomorrow," says Jani.
With rain predicted for Thursday qualifying, and plenty of incidents among the 60-car field, the big guns all went for their hot laps early in qualifying.
Jani did the best job in a well-tweaked Porsche to lap in 3 minutes 19.733 seconds at an average speed of 245.6km/h, edging Bernhard by just 0.470 seconds. Stephane Sarrazin was the quickest Toyota driver on 3:20.737 with Lucas di Grassi best of the Audi men with a time of 3:22.466.
The weather forecast for the race weekend is mixed, with a strong likelihood of rain showers, which means far more worries and variables for the teams and drivers.
"It adds a lot more stress, and a lot more decisions into the equation," says Webber.
"You need cool heads. It's such a long race. Just navigate your way through."
Briscoe is also looking good, although Dirk Muller - in another of the Ford GTs created to celebrate Ford's outright victory at Le Mans with its GT40 in the 1960s - snatched top spot.
"I got my clear lap at the end. Then, finally, the last lap was it," says Muller.
"I'm a happy man right now."