Renault has offered no guarantees that early-season engine problems will not resurface at Sunday's race in Bahrain.
Red Bull have criticised the French suppliers, believing engine problems have resulted in them only picking up 13 points in the constructors' race. Their driver Daniil Kvyat had to retire in China last week with engine trouble.
"Due to logistics of back-to-back races a complete guarantee will be hard," said Renault chief Cyril Abiteboul.
He added: "We have made improvements."
Kvyat's race ended in China when he pulled up with smoke spewing from his Red Bull, while Toro Rosso's Max Verstappen, whose car also uses a Renault engine, stopped on the main straight.
Abiteboul said Renault had made progress in performance and driveability since the opening race in Australia.
"It's frustrating that the reliability issues of Shanghai threw a cover over these," he said.
"We don't take the issues we have seen lightly, but we have taken genuine steps forward and need to focus on our continuing programme of improvements while addressing the reliability concerns in parallel."