Voters are heading to polls across the United States Tuesday to cast their ballots in the midterm elections at a time when Republicans are expected to make major gains against the majority-Democrat Congress.

A man arrives to cast the ballot during the midterm elections at a polling station in the City Hall of San Francisco, the United States, Nov. 2, 2010. [Liu Yilin/Xinhua]

Across the country, polling stations opened early Tuesday morning and will close between 6 p.m. and 9 p.m., and Americans are voting in nearly 500 Congressional races nationwide.

Washington D.C.

In the Washington, D.C. area, people were seen standing in line at 7:00 a.m., while it was still dark, ostensibly to cast their votes before heading off to work.

U.S. mid-term elections

Jim Harf, a voter who spoke with Xinhua reporters outside a polling station, said the economy is the main issue in these elections.

"The economic issue here has overridden every other issue, whether health care or Afghanistan, or Iraq, or other problems," he said.

Indeed, many Americans are angry that U.S. President Barack Obama's policies have done little to boost employment at a time when the jobless rate hovers near the double digits.

And that is the main reason why Republicans are expected ride in on a crest of voter frustration to win control of the House of Representatives and narrowly miss taking the Senate from the majority Democrat Congress.

They must win 39 seats to gain the majority in the House, which is highly likely, according to polls and experts. In the Senate, Democrats are predicted to cling to a slim majority.

Americans are also concerned about the ballooning deficit, as Obama passed a nearly 1 trillion U.S. dollar stimulus package last year in a bid to stabilize the economy. While many economists said the package prevented the country from plunging into another Great Depression, voters are concerned that they will have to pick up the tab later. Many also note that the stimulus failed to create the jobs the president said it would.

"For me the major issue is government spending," said Ben Owens, another voter.

Many have also voiced concern over what experts said is the most contentious Congress in years, as Democrats and Republicans are at each others' throats and unwilling to cooperate on most issues.

"I'm concerned about a divided Congress and one that doesn't compromise," said Sarah, who did not give her last name, "Regardless of who wins it's definitely important that they work together. Nothing gets done if it's divided and people are blocking things left and right."