MONTREAL, Canada - Struggling Red Bull has a high mountain to climb butcan still reach the Formula 1 summit by the end of the 2014 season for a fifth consecutive Drivers' crown.That's the view of team principal Christian Horner, given ahead of this weekend's (June 8) Canadian Formula 1 GP.Mercedes has dominated the '14 season so with six wins from six races; Horner and his four-times champion Sebastian Vettel were not, however, giving up hope. "Nobody is chucking in the towel," said Horner, that even if the standings suggest the title has become a duel between Mercedes team mates Lewis Hamilton and Nico Rosberg.'NOBODY IS GIVING UP'Rosberg leads overall with 122 points to Hamilton's 118, thanks to his winning in Monaco two weeks earlier, with Australian youngster Daniel Ricciardo on only 54 as the closest Red Bull driver."We have a mountain to climb," Horner said. "Take nothing away from Mercedes, the team has done an incredible job this year, but as we've seen in previous years, Red Bull had a difficult start in 2012 and managed to turn that around."Nobody is giving up on anything."Mercedes has a hefty 240 points in the Constructors' standings; Red Bull is second but way behind on only 99 and has been playing catch-up with an under-powered Renault 'power unit' but there have been signs of progress. Ricciardo made it to the podium at the previous two races - thirdin Spain and Monaco.'NO ULTIMATUMS'The Australian is fourth overall, German Vettel is back in sixth. An unfamiliar position for a team that's won both titles for the previous four years but Horner underlined his faith in Renault, denying rumours that the team was considering its engine options."Renault fully understands out predicament," Horner added. "There are no ultimatums for Renault other than we want to improve as quickly as we can."We've enjoyed a great deal of success with Renault over the years. All Red Bull's champions and victories have come with Renault engines and we trust in them to sort out their issues."