Alonso is four points ahead of Red Bull's double champion Sebastian Vettel with five races remaining worth a total of 125 points.
Red Bull swept the front row in qualifying, with Australian Mark Webber on pole, but Alonso will line up fourth on the starting grid - right behind Vettel - and the Spaniard told reporters there was everything to play for.
"I am not worried for tomorrow, I am not worried for the next five races," he said after a qualifying lap time three tenths slower than Webber's best.
"It will be tight, as we knew. They (Red Bull) have one advantage, that is the car. We have the one advantage, that is the team. So we will see."
The Ferrari has looked a lot more competitive in South Korea than it was in Japan last weekend, where Alonso spun off at the first corner after making contact with Lotus's Kimi Raikkonen and retired with a puncture.
Alonso had started sixth in that race.
The double world champion said it had been a surprise at Suzuka to see Red Bull, who have had the benefit of a new rear wing 'Double DRS' system for the last two races, out of everyone's reach but felt Japan might have been a perfect track for them.
Korea, he felt, was more normal - even if his rivals had been fastest in practice and through all the three stages of qualifying.
"I am reasonably confident to do a good race, the long runs normally are good for us. Yesterday was good and in the race pace there are many factors," he declared.
"In qualifying there is only the quickest car, doing pole position. In the race it is not only the quickest car. You need to have a good strategy, good tyres, good pitstops, good start. So many things.
"In that, in general, I think we are the strongest team. With all these factors, and thanks to this strength, we are leading the championship."
(Reporting by Alan Baldwin, editing by John Mehaffey)