Ferrari have set off "alarm bells" at triple back-to-back world champions Mercedes, team chairman and co-owner Niki Lauda has admitted.
Sebastian Vettel and Lewis Hamilton traded victories in Melbourne and China, but it was Vettel's win last weekend in Bahrain that has Mercedes worried, according to Lauda.
"The alarm bells are ringing with us," he told newspaper Osterreich.
"Those who win in Bahrain have a certain buffer for the next three races."
Both Hamilton and his Mercedes teammate Valtteri Bottas admitted in Bahrain that the main problem with the 2017 car is the new Pirelli tyres, particularly in hotter weather.
The championship continues on April 30 with the Russian Grand Prix.