US President George W. Bush and his Democratic challenger John Kerry claimed victories one after another in a fierce contest to win the presidential race on Tuesday, but there is no surprise outcome yet in the changing tally.

According to the latest statistics, polls closed in more than two dozen states but the race remains wide open.

Currently, all the battleground states remain undecided. It was too close to call in the most competitive states of Ohio, Pennsylvania and Florida, with a combined 68 electoral votes.

There are altogether 538 electors and a minimum of 270 electoral votes is required to win the Electoral College.

Earlier, Bush, 58, won West Virginia, a state with five electoral votes and a long history of backing Democrats until Bushtook it in the 2000 election.

For now, Bush has won 16 states, namely Alabama, Georgia, Indiana, Kansas, Kentucky, Nebraska (4 of the 5 electoral votes), North Carolina, North Dakota, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Virginia, West Virginia and Wyoming for 155 electoral votes in total, networks exit polls projected. All of them were won by him in the 2000 presidential election.

Kerry, 60, has won 112 electoral votes from the District of Columbia and Connecticut, Delaware, Illinois, Maine (3 of the 4 electoral votes), Maryland, Massachusetts, New Jersey, New York, Rhode Island and Vermont. All of them were claimed by Democratic presidential candidate Al Gore in last presidential election.

American voters started casting their ballots on Tuesday morning, as polling stations were opened at 6 a.m. or 7 a.m. EST (1100 or 1200 GMT) in the states along the east coast. All voting, except in Alaska and Hawaii, were to close at 11 p.m. EST (0400 GMT, Wednesday).

Bush cast his ballot at his hometown of Crawford, Texas, Tuesday before flying to Washington, and Kerry voted in Boston, Massachusetts.

In the general elections, voters will also elect a vice president, 34 senators who account for one-third of the Senate, all the 435 representatives and 11 governors.

Republicans now hold 227 of the 435 House seats while Democratshold 205 seats and have the support of the House's lone independent, Bernie Sanders of Vermont.

Preliminary results so far of Senate races showed a tie between Republicans and Democrats, with each side winning five states.

Republicans defeated Democrats in Georgia, Ohio, Missouri, New Hampshire and Alabama, while Democrats registered victory over Republicans in Vermont, Indiana, Connecticut, Illinois and Maryland.

In the Senate races, 34 of the 100 seats in the Senate are at stake, 19 held by Republicans and 15 by Democrats. Currently, Republicans enjoy a majority with 51 seats, with 48 of the rest going to Democrats and one to independents.

According to the country's election system, Americans do not directly choose the president. Instead, after ballots are counted in each state, state representatives, called electors, will vote on the basis of the state tallies in an Electoral College, a system which has been operating since 1788.

It was likely that 58-60 percent of eligibles, or 117.5-121 million voters, would vote at about 200,000 polling stations across the country this year, higher than in 2000 when 54 percent of the electorate, or 105.4 million voters, went to the polls.

Results of the voting were expected late Tuesday night or early Wednesday morning.

If no candidate receives a majority, the House of Representatives -- one of the two chambers of the US Congress -- must determine the winner from the three candidates who received the most votes in the Electoral College.