The Australian was a close second quickest in second practice in Austin, finishing just 0.194s behind pace-setter Nico Rosberg.

Ricciardo admitted the day had been very smooth for Red Bull, and he reckons the team's pace over long runs means fighting Mercedes for victory could be possible.

"I think it is one of our best Fridays for sure," said Ricciardo. "Our long run pace looks like we were able to match them if not be quicker. But I have said it before.

"It is Friday, but it is nice to have a good Friday. It is nice to start the weekend on the right foot, so I don't think we will have hours and hours of work ahead of us tonight, just a bit of fine-tuning as always and we don't have to search for too much at the moment.

"It was a good day. I think this morning was solid and the long run pace was good. Then we sort of continued on this afternoon, made a few changes in between the two sessions and we look pretty good for now.

"Hopefully we stay like that and we should have a good race if that is the case."

Ricciardo reckons Red Bull still has room for improvement in qualifying trim.

"The low fuel pace, I think it was okay," he said. "I think we can still find a bit more but I think Mercedes can also have a bit more.

"Looking at Ferrari, it was a solid pace, our long run pace I am happy with that, and we got some good consistent laps out of it and were able to chip away the whole day, so we made progress from P1 and are happy."

Teammate Max Verstappen, fifth today, was also encouraged by Red Bull's long-run pace, but also said the short runs needed improving.

"The short run for me was not great in P2. We made quite a bit of changes in the car and it didn't seem to work so that is why it took me a bit longer to go out on long run as we made quite a few changes back to what we thought could work and it worked pretty well," he said.

"I had a Ferrari in front of me and was catching him on long runs so that was positive."

Additional reporting by Jonathan Noble