The Arab Spring is widely tipped to be recognised with the Nobel Peace Prize on Friday, but Africans, from Liberia, or perhaps Sudan, offer a strong challenge that may have more global appeal for the judges.

With no woman winning the award for seven years, there are also a number of strong female contenders for 2011.

The head of the Norwegian Nobel Committee, who will announce the winner of the $1.5 million prize at 0900 GMT, gave little away in interviews with Norwegian broadcasters, though he took care to seem to steer questions away from a single-minded focus on Arab pro-democracy demonstrators.

"There are many other positive developments this year that we have observed in the international community," former prime minister Thorbjoern Jagland said on Thursday. "I think it is a little bizarre that researchers and others have not seen them."

"The theme we have chosen is a very important theme, and a very important driver in the world community today, which can be associated with many things, maybe ... also the Arab Spring," he told public television NRK early on Friday.

"We have been looking at a much bigger picture while researchers in a way have only picked out a few people and then that has continued to roll in the media. We hope to support something which is very important in the world community today.”

For some observers, including Norway's often well-informed TV2, that could point to a woman winner.

Faced with a host of nominations each year to benefit from the bequest left by the Swedish inventor of dynamite, Alfred Nobel, the five Norwegian committee members, appointed by the parliament in Oslo, generally tend to seek diversity from year to year in the characteristics of the peace prize winner.

TV2's favourite, in a broadcast late on Thursday, was Liberian President Ellen Johnson-Sirleaf, the first elected female head of state in Africa, who is running for re-election next week and is widely seen as a pioneer for women's rights.

The economic and political empowerment of women, notably in developing countries, is cited by many researchers as a positive factor in reducing conflict and improving prosperity.

Many candidates

Several of those nominated for the prize as leading lights in the Egyptian and Tunisian protest movements are women -- Asmaa Mahfouz and Israa Abdel Fatah of Egypt's April 6 Youth Movement Facebook group and Tunisian blogger Lina Ben Mhenni are among nominees who might be part of an Arab Spring award.

But the difficulty of identifying a clear individual, or even formal group, which might receive the prize on behalf of the Arab Spring movements, may discourage the committee -- as might continued uncertainty about the impact of the changes, both in Egypt and Tunisia, as well as in Libya, Syria, Yemen and elsewhere, where bloodshed is continuing.

Egyptian men Ahmed Maher and Google executive Wael Ghonim, arrested for trying to help keep social media alive during the protests, are also cited among potential laureates. Afghan Sima Samar is another contender, for her efforts to improve women's rights and access to healthcare.

The secession of South Sudan after years of conflict might also be a contender for recognition, though precisely who would be honoured is unclear. The arrest this year of the last major war crimes suspects from the fighting in the former Yugoslavia could be reason to honour the court which has tried them.

The list of possible recipients of the committee's annual favour is almost endless, however, ranging from Europeans like former German chancellor Helmut Kohl and the European Union itself to Cuban dissidents and a Vietnamese monk.

It is unlikely, Jagland said, that the choice will prove as controversial as the first two laureates named during his time as chairman of the panel -- Barack Obama, honoured in 2009 after less than a year as U.S. president on the strength of promises he made, and last year's winner, jailed Chinese dissident Lu Xiaobo, whose recognition infuriated Beijing.

"This is a very strong Nobel Peace Prize for many people, but it is a consensual one for the international community," Jagland said. "It is not uncontroversial but it will not create as much reaction from one country as it did last year."

Former US president Jimmy Carter, who won the Peace Prize in 2002, told Reuters on Thursday that Obama still had to fulfil the promises which had earned him the award two years ago. He said that last year's recognition of Lu may well have a positive effect for rights in China, despite the public anger.

As for predicting a winner this year, however, Carter echoed many seasoned Nobel-watchers: "I have no idea," he said. "I didn't know when I got it." – Reuters