YEONGAM, South Korea: Red Bull boss Christian Horner says that title success this year would be the team's "biggest victory" in Formula One, calling the current campaign the toughest in years.

The Austrian-owned outfit is chasing a third constructors' title on the bounce, as is Sebastian Vettel in the drivers' championship.

Horner believes that the way Red Bull have fought back this season after an indifferent start would make a hat-trick of titles all the sweeter. They top the constructors' standings from perennial rivals McLaren.

"I think it would be our biggest victory in many respects because it doesn't get easier," Horner was quoted as saying by the Autosport website.

"2010 was a phenomenal achievement and the realisation of having achieved it, while in 2011 we defended the title better than we won it.

"This year with the regulation changes we achieved over the winter there has been a real challenge, so whoever wins this championship is going to be very deserving because it has been one of the toughest years in recent F1 history."

Red Bull, who made their debut in 2005, and Vettel dominated the last two seasons.

They have not had it all their own way this year, but still lead the constructors' championship by 41 points with five races to go, starting with the Korean Grand Prix on Sunday.

Vettel is the man in form and has cut the lead of Ferrari's Fernando Alonso in the drivers' standings to just four points.

Many observers believe the German is now favourite, but Horner urged caution. "The only thing we have seen this year is that it is impossible to make predictions," he said.

"We've had two strong races in Singapore and Suzuka, there are five races to go and we are just taking the remaining five races one race at a time.

"So, to be honest, I don't think anybody has any real clarity as to how they are going to perform this weekend."

He added: "It was great to get back-to-back victories in Suzuka and Singapore and it was important for Sebastian to take a healthy amount of points out of Fernando." -AFP

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