President George Bush has publicly congratulated president-elect Barack Obama on his historic victory.
He vowed "complete cooperation" as the first black United States president moves into the White House.
Mr Bush has said he and Mr Obama will discuss issues such as the global financial crisis and the war in Iraq "early next week".
In a speech at the White House, Mr Bush congratulated the president-elect and said he would make every effort to ensure a smooth handover on 20 January.
President Bush said he had also spoken to Senator John McCain and congratulated him on running a determined campaign with Governor Sarah Palin of Alaska.
"No matter how they cast their ballots, all Americans can be proud of the history that was made yesterday," said the president. "Many of our citizens thought they would never live to see that day.
"This moment is especially uplifting for a generation of Americans who witnessed the struggle for civil rights with their own eyes - and four decades later see the dream fulfilled," he said.
Mr Bush has requested $US8.5 million in funding from his 2009 budget for the transition.
He also created a special transition commission in early October to brief the incoming administration.
US TV networks said on Wednesday that Senator Obama won the popular vote by 52% to 46%.
According to Fox News, the tally was 62.95 million for Senator Obama and 55.75 million for John McCain.
NBC reported that Senator Obama received 62.98 million votes nationwide and Senator McCain, 55.78 million.
As of 1630 GMT on Wednesday, with results given in 48 states and the District of Columbia, Senator Obama had secured 349 Electoral College votes, compared with 163 for Senator McCain.
Missouri and North Carolina remained too close to call.