Fernando Alonso believes Renault are unlikely to be able to match the pace of the leading teams next season, despite the regulations changes that will be introduced.
"Honestly I think it's difficult, because although there are going to be completely new rules... Next year there could be changes, but I've never seen a car that's fighting at the back one year then sweep the field the next," Alonso told Cadena Ser radio.
"It's always step by step. So it's hard to close the gap, whether it's the aerodynamics, the engine, or the tyres. Whatever our problems are, we'd have to work very hard to close that gap.
"But, to be honest, it's going to be difficult to move ahead of them (top teams), and to make a car that will be superior to theirs."
Renault, world champions in 2005 and 2006, have failed to make an impression this season and have scored just one podium in 11 races.
They are 80 points behind leaders Ferrari in the constructors' championship.
Renault's lack of form have fueled speculation about Alonso's future, with Honda Racing the latest team the Spaniard has been linked to for 2009.
The two-time champion said he welcomed the praise he has received from Honda figures recently, but he made it clear he is focused on doing his best for Renault.
"They have said a lot of good, positive things and I appreciate it," Alonso added. "But I'm still focused on this year. We are not going to throw in the towel, we are going to fight until the last lap."
The Spaniard also insisted he has no regrets about having left McLaren, and he claimed he prefers to achieve worse results at Renault.
"Yeah, yeah. I don't think I would have been second with McLaren," he said when asked if he preferred to be fourth with Renault than second with McLaren.
"I'm (saying that) based on the last few races of the past season, when I was finishing fourth and fifth.
"And that's not what I expected. This year I'm still finishing fourth and fifth but with a team who really want me to achieve that result."
He also said he was convinced he would not have had a chance to fight for the championship with the British squad.
"Yes, I'm convinced, yes," he said. "Because of the situation I lived towards the end of the season. I saw there was no way to get a good result, to get things on the right track.
"I didn't have the atmosphere that I like to be able to work. And I know it would have been difficult to fight (for the title)."