Portimao, Portugal - Renault and Williams unveiled their cars for 2009 Formula One season at presentations in Portugal on Monday.

The cars were rolled out at the Algarve Motor Park circuit at Portimao where F1 teams begin testing this week ahead of the season beginning March 29 in Melbourne, Australia.

Two-time world champion Fernando Alonso and Nelson Piquet Jr were joined by team boss Flavio Briatore to present the R28 which Renault hopes will mount a stronger challenge for the championship.

The colour scheme is in a more striking yellow and white with the name of new sponsors Total on the front and rear wings of the R29.

Williams test driver Nico Huelkenberg, meanwhile, wheeled out the team's FW31 in an interim dark blue livery.

Both cars will be testing alongside those of rival teams McLaren, who put its MP4-24 on the Portimao circuit on Saturday, and Toyota, who ran its TF109 for the first time at Portimao on Sunday.

Testing continues in Portugal until Thursday. In neighbouring Spain, BMW Sauber will launch its F1.09 in Valencia on Tuesday.

Ferrari was the first team to unveil its new car - the F60 - for the 2009 championship with a presentation on the internet a week ago.

Like other Formula One cars, both versions have wider front wings and higher and narrower rear wings in line with new aerodynamic regulations.

The R29 also features the shark fin engine cover that the team used for most of the 2008 season which ended promisingly with Alonso winning two of the last four races.

Williams have retained Germany's Nico Rosberg and Japan's Kazuki Nakajima as race drivers as it seeks to improve on a disappointing 2008 season.

The car is in a temporary winter testing livery, with the final 2009 colour scheme set to be presented next month. (dpa)