World champion Lewis Hamilton and team-mate Heikki Kovalainen lagged behind their rivals in testing ahead of the Australian Grand Prix on 29 March.
But Dennis told BBC Sport: “Whatever performance level McLaren have today we will be a competitive racing team.
“That means we will be fighting for the world championship.”
While Ferrari have been consistently fast during pre-season testing, McLaren appear to be some way off the pace of their main rivals.
During this week’s test in Barcelona, McLaren‘s Kovalainen was more than two and a half seconds down on Nick Heidfeld’s fastest time for BMW Sauber on Monday.
Ferrari’s Kimi Raikkonen topped Tuesday’s timesheets, while another low-key showing for McLaren resulted in Kovalainen being 1.677 seconds adrift.
Exciting news for all Ferrari fans. Massa took the new Ferrari F60 for a spin for the first time.
He said he is excited about the new F1 car and a bit surprised as well, having expected it to be bigger with huge front wings.
The car is still some way off the final version we will see in Melbourne, when the 2009 F1 season will kick off with the Australian Grand Prix.
For more information see the http://f60.ferrariworld.com/