Votes are still being counted in Florida, the last state in the presidential election in the United States.
Officials have counted about 99% of the vote with President Barack Obama ahead of Republican challenger Mitt Romney by an estimated 46,000 votes.
Florida has 29 electoral votes. A Radio New Zealand correspondent told Morning Report that the state is on a 'knife edge'.
Mr Obama pledged in Chicago early on Wednesday that the best is yet to come.
After a hard-fought campaign that highlighted America's political divide, Mr Obama, as he did four years ago, pledged to work with his opponents to reduce the deficit, to reform the tax code and immigration laws, and cut dependence on foreign oil.
"You voted for action, not politics as usual," he said.
Mr Romney echoed that call for unity as he graciously admitted defeat late on Tuesday night.
"This is a time of great challenge for our nation," he told a crowd in Boston. "I pray that the president will be successful in guiding our nation."
He warned against partisan bickering and urged politicians on both sides to "put the people before the politics."
Barack Obama won seven out of the nine key battleground states, including the deciding swing state of Ohio.
In the electoral college, he won 303 electoral votes to Mr Romney's 206.
The popular vote - symbolically and politically important, but not decisive - remains very close, with Mr Obama on 50.3% and Mr Romney on 48.1%.
Voters also left the Democrats in charge of the Senate and Republicans in charge of the House of Representatives.
Democrats won Senate seats from the Republicans in Massachusetts and Indiana.