Barack Obama has been sworn in as the first black president of the United States. He becomes the 44th president after replacing George W Bush.
Hundreds of thousands of people, bundled up against the cold and in a festive mood, packed Washington's Mall, which stretches from the Capitol to the Lincoln Memorial on the Potomac River, and along Pennsylvania Avenue to the White House to witness Mr Obama being sworn in as the 44th US president.
Mr Obama, and his wife, Michelle, along with president George W Bush and first lady Laura Bush, arrived at Capitol Hill after riding in a motorcade from the White House shortly before 5pm Irish time.
In his inauguration speech president Obama warned of “gathering clouds and raging storms” but he also delivered a message of hope.
The inauguration of Mr Obama (47) the son of a black Kenyan father and a white mother from Kansas, was full of ceremony, and held much symbolic meaning for African-Americans, who for generations suffered slavery and then racial segregation that made them second-class citizens.
Mr Obama took the oath of office with his hand on a Bible used by Abraham Lincoln at his first inauguration in 1861, standing on the western steps of the capitol, a building that was partly built by black slaves.
Some estimates put the number of people who packed the Mall and inaugural parade route at more than 2 million. Crowds clogged the city's metro rail system and thronged the security check-points.
“Every so often the oath (of office) is taken amidst gathering clouds and raging storms. At such times America had to remain “faithful to the ideals of our forbearers, and true to our founding document”, said Mr Obama during his speech.
“Today I say to you that the challenges we face are real. They are serious and they are many. They will not be met easily or in a short span of time. But know this, America - they will be met.”
Describing the challenges ahead, Mr Obama said: “That we are in the midst of crisis is now well understood. Our nation is at war, against a far-reaching network of violence and hatred. Our economy is badly weakened, a consequence of greed and irresponsibility on the part of some, but also our collective failure to make hard choices and prepare the nation for a new age."
However, he said that the American people had chosen “hope over fear, unity of purpose over conflict and discord”.
“On this day we come to proclaim an end to the petty grievances and false promises, the worn out dogmas, that for far too long have strangled our politics.”
In a bid to rebuild America’s standing oversees, Mr Obama said: “To all other peoples and governments who are watching today, from the grandest capitals to the small village where my father was born, know that America is a friend of each nation and every man, woman and child who seeks a future of peace and dignity, and that we are ready to lead once more.”
He added that earlier generations of Americans had faced down fascism and communism “not just with missiles and tanks, but with sturdy alliances and enduring convictions”.
He said: “Power alone cannot protect us.”
President Obama's election was cheered around the world as a sign that America will be more embracing, more open to change. "To the Muslim world," Obama said, "we seek a new way forward, based on mutual interest and mutual respect."
Still, he bluntly warned, "To those leaders around the globe who seek to sow conflict, or blame their society's ills on the West — know that your people will judge you on what you can build, not what you destroy."
"To those who cling to power through corruption and deceit and the silencing of dissent, know that you are on the wrong side of history, but that we will extend a hand if you are willing to unclench your fist."
Polls show widespread support for Mr Obama and optimism about the coming four years of his presidency, despite a deepening recession that has saddled the country with a $1 trillion deficit and 11 million people unemployed.
Mr Bush has left office having plumbed record lows in approval ratings.
Mr Obama, a former Illinois senator who capped a hard-fought election campaign with a comfortable win against Republican John McCain in November, has stressed that the time to party and celebrate will be short-lived.
Tomorrow he will start shepherding an $825 billion economic stimulus plan through Congress.
He faces daunting challenges -- economic turmoil, the wars in Iraq and Afghanistan, global warming, conflict in Gaza, tensions between Pakistan and India and a resurgent Russia.
But analysts say that at least for now, it will be his ability to revive the recession-hit economy that will be the benchmark by which his presidency is judged.
Mr Obama is expected to meet military commanders tomorrow to discuss the US troop withdrawal from Iraq, to fulfill a campaign pledge to withdraw all troops within 16 months.
The Democratic-led US Senate began confirming Mr Obama's Cabinet today, but it put off until Wednesday a vote on the designee for secretary of state, Hillary Rodham Clinton.
In a single unanimous vote, the Senate confirmed Steven Chu as energy secretary, Tom Vilsack as agriculture secretary, Arne Duncan as education secretary, Ken Salazar as interior secretary and Janet Napolitano as secretary of homeland security. It also approved Peter Orszag as head of the White House budget office.
Mr Obama's fellow Democrats had wanted Ms Clinton also approved today. But senator John Cornyn of Texas demanded a debate first regarding his concerns about foreign donations to a foundation created by Ms Clinton's husband, former president Bill Clinton.
A vote on that nomination was scheduled for Wednesday.
Agencies