Obama, 47, will be inaugurated the 44th US president on January 20, 2009, and inherit an economy mired in the worst financial crisis since the 1930s, two wars - in Afghanistan and Iraq and a nuclear showdown with Iran.

Television networks projected his victory over Republican John McCain after Senator Obama solidified traditional Democratic states and cut deep into the Republican territory which his rival needed to control to win the White House.

On a night of high drama after millions of people cast votes in an election that could reshape US politics, Obama won the crucial battleground state of Ohio in another devastating blow to rival John McCain, US television networks reported.

The Ohio loss is a heavy blow for McCain - no candidate has won the White House without taking Ohio since 1960.

No Republican has ever won the presidency without it.

Through the campaign, New Mexico's large bloc of Hispanic voters gave Obama an edge in the state - which carries five electoral votes - even though McCain's home state of Arizona is next door.

The swing state of Iowa gave Obama another seven electoral votes, US TV networks projected.

Agricultural Iowa has a history as a swing state, going Republican six times and Democrat four out of the last 10 presidential races.

The Iowans took an early liking to Obama, who used the state's quirky caucus system in the primaries to win a shock victory over Hillary Clinton and kick off his campaign.

Going into today's election, Obama held a strong 15.3-point lead over McCain in a polling average compiled by the non-partisan RealClearPolitics.com.

Obama was also competitive in Indiana and Virginia, formerly staunch Republican bastions.

Obama also won Massachusetts, Connecticut, Illinois, New Jersey, Maine and Maryland.

McCain captured Kentucky, Tennessee, West Virginia, South Carolina and Oklahoma, networks projected.

Another normally Republican state, North Carolina, was too close to call, as was midwestern Indiana, in another positive sign for Obama.

Late on Tuesday night (US time) defeated Republican presidential candidate John McCain called victor Barack Obama to concede defeat and to congratulate him on being the next president of the United States - and the first African-American leader.