Lewis Hamilton apologised to Kimi Raikkonen after a mistake by the Briton put both out of the Canadian Grand Prix.
Raikkonen stopped at the red light at the end of the pitlane on lap 20, but Hamilton drove into the back of the Ferrari and both men had to retire.
An unhappy Raikkonen spoke to Hamilton after the crash, pointing at the light.
Championship leader Hamilton said he had seen the red light when it was already too late.
"It wasn't a great stop. I saw the two guys in front battling in the pitlane and all of a sudden they stopped. I saw the red light but by the time I stopped it was too late," said Hamilton.
"It is a lot different if you crash into the wall and are angry, it is not like that. I apologise to Kimi if I cost him the race, but these sort of things happen.
"I would rather neither of us were out, we were so quick, I was in front. Next time."
The accident left BMW Sauber's Robert Kubica with a great chance of scoring his maiden Formula One victory.