Hockenheim - Mercedes team chief Toto Wolff has said he is concerned by Ferrari's recent surge in outright power that has given them the initiative in the Formula One world championship.
Wolff told reporters late Saturday that Ferrari had a half-second time advantage on the straights at the Hockenheimring where Sebastian Vettel delighted home fans by claiming pole for the German Grand Prix ahead of Mercedes' Valtteri Bottas.
"We were looking good through all kinds of corners, but we are not able to match their straight-line performance.
"Valtteri was exceptional in the third sector and this is why he was even closer to pole, but we just have to look at things and try to improve."
He said that Ferrari "have a great power unit... Huge performances."
Ferrari's recent performances have followed their introduction of a new engine at the Canadian Grand Prix in June while Mercedes delayed their new unit until the French Grand Prix.
Champions Mercedes had previously enjoyed an overall power advantage, which has been a key factor in their domination in recent seasons, but they no longer reign supreme and have won only one of the last five races and trail Ferrari in both the drivers and the constructors championships ahead of Sunday's race.
Wolff was not keen to support any suggestions that the new Ferrari unit's extra power has come from questionable means.
An investigation by ruling body the International Motoring Federation (FIA) earlier this season cleared Ferrari of any wrongdoing in relation to the battery.
However, the Ferrari factory team and their F1 customer teams - Haas and Force India - all gained from the introduction of new MGU-K (motor generator unit - kinetic) and energy store systems in Germany.
"I want to look at Mercedes and say is there anything that we've missed? How can we increase our power output on the ICE or from the battery or from the MGU-H?
"Whatever we can look at in order to have more power because, if we want to win this championship, or stay in the hunt of the championship, we've got a severe warning today in terms of what we've seen...."