Formula One's oldest and most successful team arrived at the scenic Spielberg track 140 points adrift of the champions, who have won all eight races this year with Lewis Hamilton and Valtteri Bottas.
Leclerc, in his first season with Ferrari, finished third and best of the rest in last Sunday's French Grand Prix.
"I think at the moment it's quite difficult. They seem very, very quick," said the 21-year-old Monegasque when asked whether Ferrari could give Mercedes a tougher time at the Red Bull Ring.
"They were extremely quick in Paul Ricard, especially in the race pace, so I think we are focusing on ourselves and trying to do the best job possible. But, to be honest, it's quite difficult to be at their level."
Leclerc is still chasing his first career win, coming close in the second race of the year in Bahrain when he led from pole only to suffer engine problems.
The youngster has been on the podium three times and sounded more hopeful after Sunday's race, in which he had chased down Bottas to finish 0.929 behind the Finn.
"I think he was struggling quite a bit on the second set of tyres with some blistering. We weren't. I think we managed quite well our race so it shows that still everything is possible but it's just very difficult," he said.
"If they don't run into issues, it's a struggle for us to challenge them. So we are just trying to do the best in our races every time.
"On my personal side, it was good to have a good weekend after a few where I've been struggling a bit more."
Also on the plus side, Leclerc said Austria was one of his favourite circuits with a short lap that reminded him of his days in go-karts.
"I just enjoy driving here," he said.
Asked about the championship, Leclerc said Ferrari would not give up until it was mathematically impossible to overhaul Mercedes.
(Reporting by Alan Baldwin in London, editing by Ed Osmond)
