Voter turnout appeared to be high in many parts of the United States, with long waits at some polling places.

Election observers reported sporadic problems around the country, with long waits, broken machines and displaced voters affected by Superstorm Sandy, but as polls were due to start closing it was too early to tell how much of an impact the issues would have on the overall result.

After months of candidate visits, campaign bitterness and a barrage of costly television ads, Florida was poised on Tuesday to play a crucial role in picking America's next president.

The state has 29 electoral votes up for grabs, the most of any swing state, and both President Barack Obama and Republican Mitt Romney worked hard here until the final moments of the campaign.

Turnout appeared to be heavy, with long lines reported in many places, even though more than 4.5 (m) million people out of nearly 12 (m) million registered voters cast ballots early.

Anyone in line when the polls close at 7 pm EST (0000GMT) will be allowed to vote Tuesday, Florida officials said.

There were reports of sporadic, but mostly minor problems at the polls on Tuesday.

One Florida elections office mistakenly told voters in robocalls the election was on Wednesday.

Another office lost power for about 45 minutes.

Florida, with its diversity, wealth and political cache has long been seen as a toss-up by political experts.

Obama won here in 2008, but since then, the state's unemployment and foreclosure rates have remained above the national average.

Another win in Florida would all but assure Obama four more years in the White House.

Turnout for the election also appears to be high so far in parts of New York, including areas ravaged by superstorm Sandy last week.

Obama is expected to easily capture New York's 29 electoral votes in his race against Republican challenger Romney.

In Harlem, intermittent ballot scanning problems caused delays for about a dozen voters.

Poll worker, Carolyn LouAllen, admitted that some scanners were "breaking down" and it was "hard getting in touch with people at the main office."

But many, including New York City voter Ethan Newlin, said the scanners appeared to be working, "just fine."

Workers answering phones at the Election Protection call centre in New York City said they received more than 5,500 calls from New Jersey residents who were encountering issues, many of which dealt with voters displaced by Hurricane Sandy having trouble finding polling stations.

Election Protection Lead, Catherine Weiss, described it as an unusually high volume of calls from voters in New Jersey.

She said it was "two or three times at least the normal volume," even though the state had made provision for displaced New Jersey residents.

Many people across New Jersey who lost their homes in last week's megastorm or are still without power went the extra mile, literally, to get out and vote Tuesday.

For Point Pleasant voter Danielle Carr it was a relief to be able to vote,

"It was quick and easy, " she said. "We went in and voted right away and I'm just happy to be able to do it because I was worried we weren't going to be able to."

As tough as his personal situation is, with a damaged business and destroyed home, Lou Mercatanti, "wanted to vote under any set of circumstances."

Jean Marie Payne, bought her daughter to vote, making the point that "even if there are things going on around you, you have to take a moment just to voice your opinion and voice, you know, the things that really matter to you."