Mercedes now the underdog in F1 title fight - Wolff

The reigning world champion team trails rival Ferrari by 17 points in the constructors' championship, having scored three wins in six races.

At this point last year, it had won five from six and led Ferrari by 67.

In the drivers' championship, Sebastian Vettel leads Lewis Hamilton by 25 points, with Mercedes non-executive chairman Niki Lauda saying his team's title ambitions are over unless the former retires at least once.

When asked by Motorsport.com if Mercedes was the underdog given the current state of play, Wolff said: "I like the notion of underdog, because the underdog is the one people want to see win.

"As a matter of fact, I think we've been that since the beginning of the season. We have been dropping in and out of the tyre window, we never had two drivers or two cars over the course of the weekend within that window.

"We saw an exceptional performance of Valtteri [Bottas] in Sochi, that we weren't able to replicate on Lewis' car. We've seen and exceptional performance from Lewis in Barcelona and that inconsistency has been following us through the season.

"On the opposite side, Ferrari put the car on track in Barcelona and they were quick from the get go, so yes, we are the underdog. We need to catch up and this is the reality at the moment."

Mercedes is not enjoying the performance advantage it has had in recent seasons while its core problem is getting its tyre working, particularly the ultrasoft.

With Ferrari a regular threat, the Italian team is able to take advantage on the low-energy tracks its SF70H has proven to have a broader working range on.

When it was put to him that it was ironic Mercedes was struggling with its tyres as it was one of three teams - Ferrari and Red Bull were the other - to carry out 2017 tyre testing, Wolff said: "I'm not sure if it was a benefit or not.

"In the end, how the chassis interacts with the tyres is a complex subject. There are many dozens of factors that interact and make it perform or not.

"This is not about seeking an excuse because others are able to extract the performance of the tyres and we don't. We have seen from some our competitors, like Red Bull, they have been far out of the window, one-and-a-half seconds off the pace.

"Then back in the race, you could see they are performing well. It's a problem that seems to hit everybody but not Ferrari. All credit to them - they have a solid car that is capable to cope with the tyres."