Kimi Raikkonen says Ferrari's performance is too inconsistent from circuit to circuit this year to mount a proper challenge to Mercedes.
Ferrari has yet to win a race this season but has finished every round bar Monaco on the podium. However, the pace relative to championship leaders Mercedes has fluctuated from race to race and Raikkonen says the key to success is ironing out the peaks and troughs.
"At the moment it varies a lot depending on places, layouts, conditions, but we have to really challenge them everywhere, so we have things to improve," he said.
The gap in qualifying at the Canadian Grand Prix was less than 0.2s, but just one week later at the Grand Prix of Europe in Baku the deficit had grown to more than 1.2s.
"If you take purely the results of the last couple of races then I would say we were closer to them in Canada than Baku. But things change a lot between different circuits and different conditions and for sure Baku wasn't the easiest circuit for us as we struggled quite a bit in certain areas.
"In the end we managed to turn things around [in the race] but for sure we still have quite a bit of work to do, in order to be able to challenge them in every race and every condition -- it doesn't matter where we go, we have to challenge everywhere."