terror attacks. The Nobel committee praised Obama's creation of "a new climate in international politics" and said he had returned multilateral diplomacy and institutions like the U.N. to the center of the world stage.
"You have to remember that the world has been in a pretty dangerous phase," Jagland said. "And anybody who can contribute to getting the world out of this situation deserves a Nobel Peace Prize."
Until seconds before the award, speculation had focused on a wide variety of candidates besides Obama: Zimbabwe's Prime Minister Morgan Tsvangirai, a Colombian senator, a Chinese dissident and an Afghan woman's rights activist, among others. The Nobel committee received a record 205 nominations for this year's prize, though it was not immediately apparent who nominated Obama.
"The exciting and important thing about this prize is that it's given to someone ... who has the power to contribute to peace," Norwegian Prime Minister Jens Stoltenberg said.
Archbishop Desmond Tutu of South Africa, who won the prize in 1984, said Obama's award shows great things are expected from him in coming years.
"It's an award coming near the beginning of the first term of office of a relatively young president that anticipates an even greater contribution towards making our world a safer place for all," Tutu said. "It is an award that speaks to the promise of President Obama's message of hope."
Obama is the third sitting U.S. president to win the award: President Theodore Roosevelt won in 1906 and President Woodrow Wilson was awarded the prize in 1919.
Wilson received the prize for his role in founding the League of Nations, the hopeful but ultimately failed precursor to the contemporary United Nations.
The Nobel committee chairman said after awarding the 2002 prize to former Democratic President Jimmy Carter, for his mediation in international conflicts, that it should be seen as a "kick in the leg" to the Bush administration's hard line in the buildup to the Iraq war.
Five years later, the committee honored Bush's adversary in the 2000 presidential election, Al Gore, for his campaign to raise awareness about global warming.
In July talks in Moscow, Obama and Russian President Dmitry Medvedev agreed that their negotiators would work out a new limit on delivery vehicles for nuclear warheads of between 500 and 1,100. They also agreed that warhead limits would be reduced from the current range of 1,700-2,200 to as low as 1,500. The United States now has about 2,200 such warheads, compared to about 2,800 for the Russians.
But there has been no word on whether either side has started to act on the reductions.
Former Peace Prize winner Mohamed ElBaradei, director general of the International Atomic Energy Agency in Vienna, said Obama has already provided outstanding leadership in the effort to prevent nuclear proliferation.
"In less than a year in office, he has transformed the way we look at ourselves and the world we live in and rekindled hope for a world at peace with itself," ElBaradei said. "He has shown an unshakable commitment to diplomacy, mutual respect and dialogue as the best means of resolving conflicts."
Obama also has attempted to restart stalled talks between the Israelis and Palestinians, but just a day after Obama hosted the Israeli and Palestinian leaders in New York, Israeli officials boasted that they had fended off U.S. pressure to halt settlement construction. Moderate Palestinians said they felt undermined by Obama's failure to back up his demand for a freeze.
Obama was to meet with his top advisers on the Afghan war on Friday to consider a request by Gen. Stanley McChrystal, the U.S. commander in Afghanistan, to send as many as 40,000 more troops to Afghanistan as the U.S war there enters its ninth year.
Obama ordered 21,000 additional troops to Afghanistan earlier this year and has continued the use of unmanned drones for attacks on militants in Afghanistan and Pakistan, a strategy devised by the Bush administration. The attacks often kill or injure civilians living in the area.
Nominators for the prize include former laureates; current and former members of the committee and their staff; members of national governments and legislatures; university professors of law, theology, social sciences, history and philosophy; leaders of peace research and foreign affairs institutes; and members of international courts of law.
In his 1895 will, Alfred Nobel stipulated that the peace prize should go "to the person who shall have done the most or the best work for fraternity between the nations and the abolition or reduction of standing armies and the formation and spreading of peace congresses."
The committee has taken a wide interpretation of Nobel's guidelines, expanding the prize beyond peace mediation to include efforts to combat poverty, disease and climate change.
The Norwegian Nobel Committee decided not to inform Obama before the announcement because it didn't want to wake him up, committee chairman Thorbjoern Jagland said.
"Waking up a president in the middle of the night, this isn't really something you do," Jagland said.
Read the 2009 Nobel Peace Prize citation