Former vice president Al Gore endorsed Illinois Senator Barack Obama at a rally Monday in Detroit for the Democratic Party's presidential candidate. ( dpa )
"I speak to you as a citizen of the United States ... and a citizen of the world," Gore told Obama supporters.
Winner of an Oscar for his climate-change documentary An Inconvenient Truth and a Nobel Peace Prize laureate for his campaign to publicize global warming, Gore declared that the outcome of the 2008 election would effect the future of the planet.
A former US senator and Bill Clinton's vice president from 1993- 2001, Gore was the Democratic presidential nominee in 2000, winning the popular vote but losing the decisive electoral college count to George W Bush by the disputed, 500-vote margin in the notorious Florida election.
Gore said that the 2008 race, in which Obama is the presumptive first-ever African-American major-party presidential nominee, has "reinvigorated the country."