Re-elected US president Barack Obama today told ecstatic supporters the “best is yet to come” in a victory speech in his home city of Chicago.

Flanked by wife Michelle and daughters Malia And Sasha, the jubilant Democrat congratulated opponent Mitt Romney on a “hard fought campaign” and revealed he would work with the former Massachusetts governor to take the country forward.

The president told the crowd, who chanted "four more years" as he arrived on stage, that they had "lifted me up the whole way and I will always be grateful".

And he heaped praise on his family, revealing he had never loved his wife Michelle more and commending his "smart, beautiful" daughters.

President Obama vowed to revive America's economy but warned "progress will come in fits and starts".

Rival Mitt Romney earlier conceded defeat, phoning the president to congratulate him on his victory.

He told his supporters he and running mate Paul Ryan had "given our all" to the campaign and said he wished his Democrat opponent well.

The businessman urged his supporters to pray for the re-elected president as he returns to the White House against a backdrop of economic gloom.

He added: "I so wish that I had been able to fulfil your hopes to lead the country in a different direction but the nation chose another leader and so I join with you to earnestly pray for him and for this great nation."

Although polls put the two candidates neck and neck, Obama secured a convincing victory. Under the electoral college system, which allots votes to states according to population size, he has 303 while Romney is on 206, with Florida yet to declare.

At his headquarters in Boston, Massachusetts, Governor Mitt Romney addressed a ballroom full of the Republican party faithful to thank them for their support and offer his congratulations to President Obama.

He told them: "Thank you my friends, thank you so very much. I have just called President Obama to congratulate him on his victory. His supporters and his campaign also deserve congratulations.

"I wish all of them well, but particularly the president, the first lady and their daughters.

"This is a time of great challenges for America, and I pray that the president will be successful in guiding our nation."

Today David Cameron sent his congratulations to Barack Obama, saying: "I think he's a very successful US president and I look forward to working with him in the future."

Speaking during a tour of the Middle East, the Prime Minister said: "I would like to congratulate Barack Obama on his re-election.

"I have really enjoyed working with him over the last few years and I look forward to working with him again over the next four years.

"There are so many things that we need to do: we need to kick start the world economy and I want to see an EU-US trade deal.

"Right here in Jordan I am hearing appalling stories about what has happened inside Syria so one of the first things I want to talk to Barack about is how we must do more to try and solve this crisis.

"Above all, congratulations to Barack. I've enjoyed working with him, I think he's a very successful US president and I look forward to working with him in the future."