Daniel Ricciardo may not have a car to win races in 2019, the Australian's new boss has admitted.

Ricciardo and Renault shocked the Formula 1 world recently by announcing that the 29-year-old is leaving Red Bull at the end of the year.

"His commitment to us proves our will to accelerate the catching-up process to the top teams," Renault boss Cyril Abiteboul told Auto Motor und Sport.

"It's also a recognition of the work we have done over the past two-and-a-half years.

"Daniel's talent and charisma are a big bonus for us. We have to repay that trust by providing him with the best possible car."

However, Abiteboul acknowledges that Ricciardo may not be in a winning position until 2020 or 2021.

"With Ricciardo, the big objective is to fight for the title in 2021, but we hope that he can start winning races in 2020," he told France's Auto Hebdo.

"But I have also realised that these 29, 30-year-old drivers - and it's the same thing with Nico [Hulkenberg] - they not only want to drive but they aspire to something else.

"It's not the same with everyone, but I do believe it is with these two guys."

Abiteboul also said that Ricciardo had "justified doubts" about Red Bull's Honda engines for 2019.