"The long term trend is that the world is indeed getting more peaceful," said Geir Lundestad, the head of the Norwegian Nobel Institute. "Still, every year (picking the winner) is difficult."
Norwegian public broadcaster NRK, often thought to have strong sources, said there would be a single winner this year, unlike 2011 when three women won, and the prize could go to the EU or to activists in Russia, Belarus or Mexico.
"The most spectacular, at least seen with Norwegian eyes, would be if the EU got the peace prize," NRK commentator Knut Magnus Berge said.
He said an award to the EU would highlight its historic role in uniting the continent after World War Two and give the bloc a lift just when the eurozone is mired in a debt crisis.
But voting for the EU could be controversial, since the committee's five members are chosen by the Norwegian parliament and Norway itself has twice voted against joining the EU.
"We all know how divided Norway is on the European Union and we all know that Norway is divided on the Middle East, very divided," Lundestad said. "If you keep the EU and the Middle East out, it's very easy."
Kristian Berg Harpviken, head of the Peace Research Institute Oslo, said a prize to the EU would be "very controversial". He told NRK the EU certainly did not deserve a 2012 prize since it was failing to sort out its problems.
Top Russian candidates include Lyudmila Alexeyeva, considered the grandmother of Russia's human rights movement, Svetlana Gannushkina and the civil rights society Memorial that she helps to lead, and Alexei Venediktov, the editor of the radio station Ekho Moskvy.
Criticism of Russia's human rights record grew louder this year as the government cracked down on free speech ahead of presidential elections. Some members of the punk band Pussy Riot were jailed for a protest in Moscow's main cathedral against Vladimir Putin, Russia's dominant leader for almost 13 years.
But picking a Russian may be politically risky as Norway has maintained healthy relations with Moscow and committee chairman Thorbjoern Jagland is also the secretary-general of the Council of Europe, which promotes human rights, democracy and the rule of law in its 47 member countries, including Russia.
A way to indirectly address the issue would be to place the award in Belarus, a close Russian ally, honoring jailed dissident Ales Bialiatski for his efforts to expose Europe's last dictatorship. Bialiatski is also considered for the European Parliament Sakharov prize.
Belarus's parliamentary elections last month were dismissed by international monitors as a sham. EU foreign affairs chief Catherine Ashton said the vote "took place against the background of an overall climate of repression and intimidation".
Although the Arab Spring pro-democracy uprisings generated a slew of nominations, recent violence and disorder have made it more difficult to honor the region's transformation, leaving some religious leaders as favored candidates.
The betting agency Unibet favored Maggie Gobran, a Coptic Christian welfare worker who runs a children's mission in Cairo, while other mentioned include Nigerian religious leaders John Onaiyekan and Mohamed Sa'ad Abubakar, who have helped to calm their country's Christian-Muslim violence this year.
The committee received 231 nominations this year, including 43 organizations. It usually narrows the list to between 25 and 35 names at its first meeting to weigh candidates.
Other betting sites favored Afghan women's rights leader Sima Samar and retired U.S. political science professor Gene Sharp, an advocate of non-violent struggle.