Lewis Hamilton admitted he did not expect he would be able to get anywhere near Red Bull's pace in United States Grand Prix qualifying.
The McLaren was the only driver who could threaten Sebastian Vettel, who had dominated practice and looked assured of pole from the outset.
Hamilton was able to push the second Red Bull of Mark Webber back to third, and got within 0.109 seconds of Vettel.
"I'm very, very happy with my lap," said Hamilton.
"I saw in Q2 they were massively quicker, a second or nine tenths. I didn't know where I would find that.
"I went into Q3 and pushed as hard as I could, and found everything. I found more time in the last sector. I did two laps consecutively and surprisingly the second lap was quicker.
"On that lap I was on the limit everywhere. I think I lost about a tenth at the last corner - I gained it on the way in and lost it on the way out - but still I'm really, really happy to be where I am."
But Hamilton acknowledged that starting on the dirty side of the grid in second place might prove to be a disadvantage.
"I am not really concerned about the first corner, I'm more concerned about the dirty side of the grid," he said.
"I did a launch from it in P3 and it is quite slippery.
"It is so wide in Turn 1, I don't think much can go wrong."