Ricciardo to leave Red Bull at the end of 2018

Ricciardo had been expected to sign a fresh deal with Red Bull, which has backed him since 2008.

When asked by Motorsport.com this week why his future had not been confirmed by the summer break as planned, Ricciardo brushed it off as just "fine-tuning" details.

Red Bull has now revealed that Ricciardo will leave the team, with confirmation of his move to Renault expected to follow shortly.

Team principal Christian Horner said: "We fully respect Daniel's decision to leave and we wish him all the best in his future.

"We would like to thank him for his dedication and the role he has played since joining the team in 2014, the highlights of course being the seven wins and the 29 podiums he has achieved so far with us.

"We will now continue to evaluate the numerous options available to us before deciding on which driver partners Max Verstappen for the 2019 season.

"In the meantime, there are still nine races left in 2018 and we are fully focused on maximising every opportunity for Max and Daniel for the remainder of the season."

Ricciardo made his F1 debut in mid-2011 when Red Bull placed him at HRT, and he joined its junior team Toro Rosso for 2012.

He spent two years there before being picked to replace Mark Webber alongside Sebastian Vettel for 2014, and won three races to Vettel's zero.

Ricciardo bested Vettel's replacement Daniil Kvyat when the four-time world champion left for Ferrari, and is level with Verstappen for wins since the Dutchman replaced Kvyat in early 2016.

However, Verstappen was awarded a lucrative new deal at the end of last year, with Ricciardo pushing Red Bull for better terms this year.

As he assessed his options beyond 2018 Ricciardo acknowledged Renault as a possible destination but the French manufacturer appeared to be too early in the rebuilding phase of its works team project.

However, Renault has been able to convince Ricciardo it offers a credible alternative to Red Bull in the short-term, with Red Bull switching to Honda engines next season after growing frustrated with Renault.

Ricciardo joining Renault would likely have him partner Nico Hulkenberg, who is under contract for 2019, although Mercedes junior Esteban Ocon was also in talks with Renault over a loan move.

The likely candidates to replace Ricciardo at Red Bull are current Toro Rosso driver Pierre Gasly and Carlos Sainz, who Red Bull has under contract but has loaned out to Renault this year.

Sainz went on loan to Renault because his immediate options at Red Bull appeared limited.

However, putting him in the senior team would rekindle the Sainz/Verstappen rivalry at Toro Rosso from 2015 to early-2016, where there was friction behind the scenes.

Gasly is enjoying a fine rookie season with Toro Rosso and went into the summer with a sixth-place finish in Hungary to add to fourth place in Bahrain and seventh in Monaco.