Double world champion Fernando Alonso says he has not yet decided whether to stay with Renault next year.
The team have been uncompetitive this season and the Spaniard is believed to have a clause in his contract that would allow him to leave for 2009.
"I do not know what can happen. At the end of the year I will see where Renault is and decide," he said.
"The car has improved and I hope that by the end of the year there will be podiums and victories."
Alonso, who has been widely linked with a move to Ferrari in 2009 or 2010, admitted he was expecting more from his return to the team with which he won the world title in 2005 and 2006.
"The truth is that it has not been good so far," conceded Alonso, who rejoined Renault after a tempestuous year with McLaren as Lewis Hamilton's team-mate in 2007.
"It's worse than we expected and we are far from fighting for the podium and victories but we have not thrown in the towel and are working on the car day and night to improve."
He is hopeful of progress thanks to some new parts that would be on the car at this weekend's French Grand Prix.
"During the week, the team have worked hard and have made improvements to the car in testing," he added. "We have made another step forward and we are on the right track."
Alonso left McLaren one year into a three-year contract after falling out with team boss Ron Dennis over what he saw as a failure to give him the treatment he deserved as a two-time champion.
Hamilton, who was in his first season in Formula One last year, finished on the podium in each of the first nine races.
But the Englishman has been less consistent this season, making a number of high-profile errors, including crashing into title rival Kimi Raikkonen's Ferrari in the pit lane in the last race in Canada.
Alonso said the dip in Hamilton's form was to be expected.
"I am not surprised at his mistakes," he stated. "What was unusual was the first nine races last year with nine podiums. Everything went for him and he was lucky. Not everything depends on the driver. This year is more normal."