Formula One: Vettel relishing breaking Mercedes stronghold in Russia

Ferrari championship leader Sebastian Vettel said Thursday he was hoping to spring "a surprise" and end rival Mercedes' three-year domination at the Russian Grand Prix on Sunday.

The four-time world champion leads this year's title race ahead of Lewis Hamilton of Mercedes by two wins to one after three races in what is shaping up to be a two-way tussle for the title.

Mercedes have won all three Russian Grands Prix held at the Sochi Autodrom -- Hamilton twice and retired Nico Rosberg once -- and have led every lap since the inaugural race in 2014.

"On paper it's been a strong track for Mercedes so they will be very strong, everything else would be a surprise," the German Vettel said on Thursday.

"I think, and I feel, there's also a couple of corners where the (Ferrari) car was already good last year.

"The DNA of the car is still in a way similar, even though obviously the rules have changed and the car feels different... there should be places on the track where we should be strong.

"There were places last year where we were weak and we hope to be stronger this year and then we'll see where we are."

Talking to reporters at the circuit, Vettel was also asked to comment on suggestions that he and three-time champion Hamilton will benefit from team orders that require their respective team-mates to act as "number two" drivers.

"I think the way we've raced in the last two and a half years, everything straightforward, sometimes it was close, sometimes was too close as well...," he said, rejecting the notion of Ferrari team orders.

Hamilton's new Mercedes team-mate Valtteri Bottas, who took over from Rosberg after the German retired days after winning last season's world title, separately said his team had not spoken to him about introducing team orders despite telling him to move over for Hamilton in Bahrain.

"Nobody has spoken to me about this and there are a lot of 'ifs' in your question anyway," he said.

"We have not had the conversation because I do not think there is any need to. This team never really has had number one or two drivers and it's not planning to."

Hamilton made clear his frustrations after the Bahrain Grand Prix last time out and stressed the need for Mercedes to produce flawless weekends if they are to stay in close contention in what looks like being a tight battle with Ferrari and Vettel over the coming months.

Bottas, twice asked to let Hamilton pass him during the last race, said he will continue to obey such instructions, but said it is within his power to make sure it is not necessary.

"If I have some issues in this race, or we are on different strategies, or Lewis is stuck behind me, or something, if the team tells me to move over I will -- because we are doing this as a team and our target is to get maximum points."