Al Gore, the presidential nominee turned anti-climate change crusader, threw his support behind Barack Obama today and vowed "to do whatever I can to make sure he is elected".

Gore previewed the endorsement on his blog before appearing alongside Obama at a rally in Detroit, the US automobile mecca that has come to symbolise the hardships wrought by rising fuel prices.

"Over the next four years, we are going to face many difficult challenges - including bringing our troops home from Iraq, fixing our economy and solving the climate crisis," Gore wrote.

"Barack Obama is clearly the candidate best able to solve these problems and bring change to America."

Gore, who fell 573 votes short of the White House in 2000 before winning the Nobel peace prize for his environmental advocacy, also urged his vast network of online backers to donate to Obama.

Gore has enjoyed an enduring appeal to the Democratic faithful, elevating him to dark-horse status during both the 2004 and 2008 presidential seasons. Gore ultimately endorsed Howard Dean for the party's nomination four years ago, a choice that bruised his political reputation after Dean lost to John Kerry.

This year most political observers predicted Gore would stay out of the battle between Obama and Hillary Clinton, due to the awkward fallout from the Dean endorsement as well as the unseemly implications of Bill Clinton's former vice president turning against his wife.

But once Clinton conceded to Obama earlier this month, the path was cleared for Gore to get behind the newly minted nominee.

Gore could become an effective campaign surrogate for Obama - particularly on the issue of combating climate change, where the author of the 1992 book Earth in the Balance can claim a far longer history of activism than Republican nominee John McCain.

Gore could also deliver a strong rebuttal to his running mate in 2000, Joseph Lieberman, who has since left the Democratic party and is now talked about as a possible vice-presidential choice for McCain.

Still, one role in which the former Tennessee senator has expressed zero interest is as an official adviser in an Obama White House. While Gore is often mentioned as a potential energy secretary or "climate tsar" for Obama, he emphasised through a spokeswoman earlier this month that he "has long since ruled out any possibility" of returning to Washington politics.