Venezuela's state-owned oil company PDVSA has agreed a long-term deal with Williams following the Formula One team's signing of race driver Pastor Maldonado.
The agreement with the world's fifth largest oil exporter was announced by the country's socialist President Hugo Chavez at a demonstration run in Caracas by his compatriot driving last year's Williams FW32.
British-based Williams, who lost several major sponsors at the end of 2010 including the Royal Bank of Scotland (RBS), said the partnership will see PDVSA's branding on the car and drivers' race overalls.
"They are a substantial partner and can make a meaningful difference to our fighting ability," said team owner Frank Williams.
Former champions Williams, the third most successful Formula One team of all time in terms of race wins, were sixth overall last season.
Maldonado, last year's champion in the GP2 feeder series where he was also backed by PDVSA, will be partnered by experienced Brazilian Rubens Barrichello in the first race of the new season in Bahrain on March 13.
The 25-year-old Maldonado drove the car around an improvised track next to a military base.
"We expect quite a difficult season, but with determination we're going to achieve many successes. Of that I am certain," said Maldonado, personally thanking Chavez.
Chavez said he has high hopes for Maldonado as an F1 driver. Addressing him and Venezuelan athletes from other sports, Chavez said: "We will do everything we can for you."
Williams chief executive officer Adam Parr was in Caracas for the exhibition, along with a crew of more than a dozen from the British team.
"Today was very exciting for us as a team to be here in Venezuela, and to be able to show the people of Venezuela what a Formula One car is like," Parr said.
PDVSA's head of corporate affairs Julio Gonzalez added: "Pastor will fly our flag this year and carry the hopes of an entire country in this new chapter of his career."