Hours after his historic inauguration as the first black president of the United States, Mr Obama appeared to quickly honour his vow to act over the terror-suspect holding camp in Cuba.
He has previously said he will close Guantanamo, home to widely criticised war-crimes trials created by former President George Bush and Congress in 2006.
It was announced as the new president danced the night away with his wife at a series of inaugural balls, and as his new team put the brakes on all pending regulations that the Bush regime tried to push through in its last days. That order went out shortly after Mr Obama’s inauguration yesterday, in a memorandum signed by new White House chief of staff Rahm Emanuel.
Aides had previously suggested that the new Commander-in-Chief would immediately launch into the job, with a raft of policy announcements expected by the end of the week.
The 47-year-old former senator was sworn in as the 44th president of the United States in front of vast crowds of people in Washington yesterday, with millions more glued to TV coverage around the world.
During his inaugural speech in Washington, Mr Obama alluded to the task before him.
In an address which impressed rather than wowed, given its speaker’s known oratory skills, the president vowed to address the challenges that faced America, a county in “the midst of crisis”, he said.
Laying out the problems, Mr Obama said the country had a “badly weakened” economy and was at war against “a far-reaching network of violence and hatred”.
He said: “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.”
It was, he said, “the risk-takers, the doers, the makers of things” who had carried the country “up the long, rugged path towards prosperity and freedom”.
“Time and again these men and women struggled and sacrificed and worked till their hands were raw so that we might live a better life.
He spoke in front of a Washington audience, estimated to be more than a million people. Many, many more were listening around the world to the new president’s words.
As such he pledged to seek “a new way forward” with the Muslim world based on “mutual interest and mutual respect”.
He said he would “begin to responsibly leave Iraq to its people, and forge a hard-earned peace in Afghanistan”.
How he intends to achieve this is likely to be high up his agenda as he comes to grips with the job ahead of him.
Today he is due to meet high-ranking military officials to discuss the Iraq war, a senior aide said.
Mr Obama is also expected to assemble a team to look at ways of moving forward the stalled Middle East peace process. He recently told USA Today that he would address the issue on “Day One” of his presidency.
An announcement on the actual closure of Guantanamo Bay and a reversal of George Bush’s overseas abortion policy have also been put forward as early contenders for policy actions.
The US military currently has charges pending against 21 men at Guantanamo and officials have said they intended to charge dozens more.
Pre-trial hearings in two cases – the trial of five men charged in the 9/11 attacks and Omar Khadr, a Canadian accused of killing a US soldier in Afghanistan – were due to take place this week.
But before setting to work on the nuts and bolts of running a country, Mr Obama will first attend a national prayer service in Washington.
The Rev Dr Sharon Watkins will deliver the sermon at the multi-faith event – the first woman to do so at the traditional inauguration event.