Ferrari's Alonso staggered but will fight on Austin, Texas (Reuters) - Red Bull's Sebastian Vettel grabbed the pole for the United States Grand Prix on Saturday, setting up Ferrari's Fernando Alonso for the knockout punch in their season-long fight for the Formula One driver's title. Round 19 of the 20-round heavyweight bout goes on Sunday at the Circuit of the Americas with Alonso staggered from a disappointing qualifying effort that will see the Spaniard start well back of his German rival in eighth place. But Alonso, the only driver who can still deny Vettel the title, made it clear his team is not ready to throw in the towel. "We knew it would be a complicated weekend but clearly today we were too slow and we will start from too far back tomorrow," said Alonso, a three-time winner this season. Having said that, the accounts are always done at the end of the race. Our aim remains unchanged and it's still possible; on Sunday all sorts of things can happen. We will push to the limit as we have done since the start of the year at every race weekend. Ferrari had produced promising times during three practice sessions on Formula One's newest venue but could not come to grip with their tyre selection during Saturday's qualifying and paid a heavy price. "A disappointing qualifying that puts us in a very difficult position in terms of the championship, given that our main rival will start from pole position," said Ferrari team principal Stefano Domenicali. The main problem was linked to tyre performance, but let's make it clear, the responsibility rests with us because the tyres are the same for everyone. We have said it often, the sums are done on Sunday afternoon. Clearly the outlook is not positive but we are well aware the situation can be different in the race. Both Vettel and Alonso have spent the week coming to grips with the new layout that revealed some of its character but still holds plenty of unknowns going into Sunday's race. Staying on a clean line will be one of the keys but being the first race on the undulating 20-turn circuit, none of the drivers seemed certain where overtaking opportunities will present themselves. "We will find out tomorrow," said Vettel. It's always difficult because difficult because we haven't been here before.