Red Bull aiming to confirm Ricciardo before break

Horner has previously said that Lewis Hamilton was the key to the driver market and, with the world champion now confirmed at Mercedes for the next two seasons, and Valtteri Bottas also signed up by the Brackley team for 2019, the door has closed for Ricciardo to switch to the Silver Arrows.

Horner is confident that he will now be able to conclude a deal with the Australian.

"I think now that Lewis Hamilton's announcement has been made you'll see everything run pretty quickly," he told Motorsport.com.

"We're aiming to have things finalised by the summer break. It will be good to go into the break with everything sorted."

Asked if it was now just a question of money – with Ricciardo wanting to be on a similar deal to teammate Max Verstappen – Horner suggested that wasn't the key factor.

"No, no. We've got two great drivers, and they both contribute exceptionally well to the team. We're very keen to retain the same line-up for the future."

Neither of the Mercedes drivers is committed beyond 2020, mainly because the sport will be entering a new era with revised commercial arrangements between teams and the F1 organisation that are some way from being finalised.

That has made it harder for teams to sign anyone for longer than two years, while drivers are wary about how the balance of power will shift between teams under new technical regulations.

"Nobody's got a contract past 2020 at the moment," said Horner. "Hopefully that situation [the commercial deals] will start to get resolved in the next six to nine months."

Ricciardo also suggested that a two-year deal would be most likely: "Depends, depends. I think with all the changes I wouldn't want to go too long-term.

"So yeah, not too long. Three's a lot. Maybe I'm on a beach somewhere in three."

Asked if Hamilton's deal would speed things along, Ricciardo denied it, saying, "No, I knew he was going to sign," adding that a deal was "no closer than last race."