Break with Bush
Soon after his inauguration, Obama requested that the military tribunals held at the facility be suspended for 120-days.
Monica Villamizar, Al Jazeera's correspondent reporting from Guantanamo Bay, said some of the relatives of those killed in the September 11 attacks were upset by the suspensions of the trials.
"They say that, after more than seven years, they were hoping for closure and prosecution," she said.
In another break with the policies of George Bush, who was faulted by critics for his lack of engagement with the Middle East for most of his presidency, Obama spoke with Middle Eastern leaders soon after he stepped into the Oval Office.
Obama called Ehud Olmert, the Israeli prime minister and Mahmoud Abbas, the Palestinian president, promising his help in consolidating the Gaza ceasefires.
"He pledged that the United States would do its part to make these efforts successful, working closely with the international community," Robert Gibbs, a White House spokesman, said.
He also spoke to Hosni Mubarak, the Egyptian president and Jordan's King Abdullah.
The new US president is expected to soon name a Middle East envoy, with George Mitchell, a former senator, widely considered to be his choice for the job.
Obama also ordered a full review of the US strategy in Afghanistan on his first day in office and told generals to move towards executing his campaign pledge to withdraw troops from Iraq.
After a meeting with Ryan Crocker, the US ambassador to Iraq, as well as members of his national security team and the top military commander in the region, Obama said he had "asked the military leadership to engage in additional planning necessary to execute a responsible military drawdown from Iraq".
Obama has said he favours a 16-month timetable for the withdrawal of US combat troops from Iraq and has pledged to boost troop numbers in Afghanistan.
Meanwhile, Hillary Clinton won overwhelming Senate approval to become secretary of state, despite renewed Republican concerns about potential conflicts of interest created by overseas fundraising by her husband, Bill Clinton, a former US president.
Obama became the first US president to be sworn into office twice after he re-took his oath of office after it became apparent John Roberts, the chief justice who administered it during the inauguration ceremony on Tuesday, had got the sequence of the famous oath wrong, causing Obama to stumble in his recital.
|Obama re-took his oath of office at the White House following his inauguration [AFP]
Roberts was called back to the White House to administer it for a second time.
With growing job losses in the US, Obama held a meeting with top economic advisers to try to chart a course for the US out of the economic crisis.
Timothy Geithner, the nominee for treasury secretary, appearing before a senate panel for a confirmation hearing on Wednesday, said the government's response would be made in the coming weeks.
Obama's advisers have been working with the Democratic-led Congress on an $825bn fiscal stimulus package.
Obama also issued orders aimed at freezing White House senior staff pay and placed tighter controls on lobbyists, banning his administration staff from receiving gifts from them.
In a bid to increase freedom of information about the presidency, Obama introduced new rules to ensure the president can no longer deny requests for information without the agreement of US government officials.