Capping a long and bitter race for the White House, Americans cast their votes on Tuesday with polls showing President Barack Obama and Republican challenger Mitt Romney neck-and-neck in an election that will be decided in a handful of states.

At least 120 million people were expected to render judgment on whether to give Obama a second term or replace him with Romney.

After two days of travel, Obama wrapped up his final campaign tour in Des Moines, Iowa, with a speech that hearkened back to his 2008 campaign.

"I've come back to Iowa one more time to ask for your vote. I came back to ask you to help us finish what we've started, because this is where our movement for change began," he told a crowd of some 20,000 people at his last rally.

Romney put an exclamation mark on his campaign with his own, rowdy late night event, in an indoor sports arena in New Hampshire.

"Tomorrow is a moment to look into the future and imagine what we can do, to put that past four years behind us and build a new future," Romney said. "Walk with me. Tomorrow, we begin a new tomorrow."

Unlike Romney, who planned several get-out-the-vote stops in Ohio and Pennsylvania on Election Day, Obama is expected to await the election results in his hometown of Chicago, Illinois.

The Obama campaign announced that the president would spend part of Election Day playing pickup basketball with friends, close advisers and campaign staff. The Obamas will have dinner at home in the Hyde Park section of Chicago.

Later, they will be joined by Vice President Joe Biden and his family, and supporters at an election night watch party at Chicago's huge McCormick Place convention center, the VOA said.

Election eve polls cemented the impression that Obama holds a slight lead in most battleground states but cannot take victory for granted.

The close race raises fears of a disputed outcome similar to the 2000 election, which was decided by the US Supreme Court. Both campaigns have assembled legal teams to deal with possible voting problems, challenges or recounts.

"Despite the weak US economy, I still hope Obama could win the race, because he is on the right track (to salvaging the US economy)," said Jonathan Steward, a Democrat, who has been involved in public policy research in China for five years.

"Romney's economic solutions are quite similar to Obama's. The question is whom the voters believe in," Steward said. "But in other aspects, Romney goes too extreme and far-right."

Steward said he tried to register online for the presidential vote, but the e-mail containing a ballot failed to reach him.

Many Chinese netizens were also heatedly discussing the US presidential poll on Weibo, a popular service in China that resembles Twitter, on the eve of the US Election Day.

"The US Presidential Election" was leading searches in the last 24 hours on Sina Weibo on Monday night, with more than 1 million posts.

"Obama, a man that moved me. I believe he will win," a Web user named Yang Chengjie said on Weibo. Others support Obama for no particular reason.

"Although I didn't spend time learning about Obama's political stance, I support him just because he is Obama," Ye Shijia also wrote on the microblog.

Agencies contributed to this story