US President Barack Obama said Tuesday he was more optimistic now than four years ago when he won the Iowa caucuses, putting him on the path to his historic victory in the White House race.
In 2008, while still a junior senator from Illinois, Iowa launched Obama on his audacious bid to become America's first black president, embracing his message of hope and change.
Running unopposed in the Democratic Party's 2012 caucuses in Iowa on Tuesday, Obama however faces a tough battle in the November presidential elections to win a second term over his eventual Republican challenger amid a sour US economy and stubbornly high unemployment.
Speaking by video conference from a hotel in Washington, he told Iowa caucus-goers that he has grown "grayer" since his 2008 win in the state over Hillary Clinton.
But when asked by one Iowan if he still believed in hope and change, Obama replied: "In some ways, I'm actually more optimistic now than when I first ran.
"We've already seen change take place. 2012 is about reminding the American people how far we've traveled."
He highlighted the end to the war in Iraq, his signature health care reform as well as pledges to make college education more affordable for all.
Still smarting from months of political battles in Washington in which Obama has seen his agenda stymied by Republicans in the House of Representatives, Obama slammed his rivals for supporting "tax cuts for the wealthiest among us."
And he stressed: "We've done a lot and we have a lot more to do. That's why we need four more years."
Early polls from the Republican caucuses in Iowa showed a tight race between former Massachusetts governor Mitt Romney, veteran Texas Representative Ron Paul and former senator Rick Santorum.
A win in Iowa can give a candidate a huge boost, and unlock key funding as they head into the state-by-state nominating process. The Republican nominee will be crowned at the party's convention later in the year.