Daniel Ricciardo will be hoping to drink out of a Renault-branded shoe next year. File picture: Aly Song / Reuters.

Munich - Daniel Ricciardo is set to join Renault from Red Bull at the end of this season in a surprise move announced by both Formula One teams on Friday.

"Daniel's signing underscores our determination to accelerate our progress towards the forefront of the sport," Renault chief Cyril Abiteboul enthused.

"Daniel's undoubted talent and charisma are a huge bonus and statement for the team. We will have to repay his faith in us by delivering the best car possible."

The 29-year-old Australian was widely expected to extend his contract with Red Bull for the coming season as race seats at other leading teams appeared unavailable. But after five years at Red Bull, he has elected to move on and will partner German Nico Hulkenberg at Renault next season. It remains to be seen where Renault's other current driver, Carlos Sainz on loan from Red Bull, ends up.

Hardest career choice

"It was probably one of the most difficult decisions to take in my career so far," said Ricciardo." But I thought that it was time for me to take on a fresh and new challenge.

"I realise that there is a lot ahead in order to allow Renault to reach their target of competing at the highest level but I have been impressed by their progression in only two years, and I know that each time Renault has been in the sport they eventually won."

Renault, which only returned to Formula One in 2016, has signed Ricciardo on a two-year deal from next season. The team won the constructors' and drivers' championships in 2005 and 2006.

Red Bull's other driver, Max Verstappen of the Netherlands, is contracted to 2020.

"We fully respect Daniel's decision to leave Aston Martin Red Bull Racing and we wish him all the best in his future," team chief Christian Horner said.

"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."

Mercedes has retained both Lewis Hamilton and Valtteri Bottas while Sebastian Vettel is still contracted to Ferrari. Ferrari's junior driver Charles Leclerc is tipped to move up from Sauber to replace the veteran Kimi Raikkonen in the other car.

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

"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."

In addition to Sainz, Pierre Gasly at Toro Rosso could also be considered for a step up to Red Bull.

F1 is presently on its mid-season break and racing resumes on August 26 with the Belgian Grand Prix. 

Ricciardo, who has won twice this season, is fifth in the standings on 118 points, 95 behind leader Lewis Hamilton.

The Australian made his F1 debut in 2011 with the now defunct HRT and also drove for Toro Rosso, Red Bull's feeder team, before being promoted in 2014.