An urgent international effort to help Nigeria find more than 200 girls kidnapped by Islamist militants is focused on providing intelligence as experts try to locate the hostages.
Amid global outrage over the kidnapping, the United States, France and Britain are sending specialist teams to Nigeria, which said London had agreed to deploy "satellite imaging capabilities."
China promised to supply "any useful information acquired by its satellites and intelligence services," according to President Goodluck Jonathan after talks with visiting Chinese premier Li Keqiang.
Extremists from the Boko Haram group seized a first group of schoolgirls in Nigeria's volatile northeast three weeks ago, saying they were holding them as "slaves" and threatening to sell them.
The militants have since kidnapped more girls in the area and attacked a village, massacring scores of civilians. The violence and mass abduction has triggered worldwide anger.
Western governments divulged few details about the precise type of support offered to Nigeria but officials said intelligence from satellite imagery and possibly drone surveillance aircraft would be a crucial element.
Washington plans to send a team of fewer than 10 military personnel as well as specialists from the Justice Department and the FBI, US officials said.
"We're moving swiftly to put in place a team at our embassy in Abuja that can provide military, law enforcement and information-sharing assistance in support of Nigeria's efforts to find and free the girls," State Department spokeswoman Jen Psaki told reporters. The United States, which like France flies Reaper drones out of Niamey in Nigeria's neighbor Niger, would not confirm if surveillance aircraft were part of the package of assistance.
"We're discussing with the Nigerian government any type of information sharing arrangements that we can agree to," Pentagon spokesman Colonel Steven Warren said.
Defense officials acknowledged the US military had relatively weak ties with Nigeria and unlike many other African states, the government in Abuja has shown little interest in major training programs.
"In the past, the Nigerians have been reluctant to accept US assistance, particularly in areas having to do with security," said John Campbell, former US ambassador to Nigeria.
"Whatever assistance we might provide and might be welcomed by the Nigerian side is likely to be essentially technical," Mr Campbell said.
Satellite imagery and other technological surveillance would likely represent Washington's primary contribution, said Brian Jenkins of the Rand Corporation think tank, a former Green Beret who used to work as an adviser for companies facing hostage situations.
At the moment, the main task is to track down where the girls are being held, he told AFP.
"The first job is to locate where they may be. Are they all assembled in a single area that can be identified? Or have they already been scattered?" he said.
The United States also could advise Nigeria if it tried to negotiate with the kidnappers, as could the teams from France and Britain, which have experience with hostage situations, he added.
With two drones based in Niger as well as troops and aircraft deployed in Chad and Benin, France is well-placed to help track the militants that operate throughout the area, analysts said.
"It's an area we know well and where our intelligence services are active," said Eric Denece, director of the French Center for Research on Intelligence.
French support also presents a chance "to return a favor" to Nigeria, which helped in the release of French hostages abducted in Cameroon by Boko Haram, said defense expert Pierre Servent.
Some US lawmakers have suggested staging a rescue mission, but Western officials made clear there was no plan at the moment to organize such a dangerous operation.
"This is not something where the US has some magic. This isn't a rescue of a captain and his crew on a ship in the Indian Ocean," Mr Jenkins said.
"The idea that the US will just intervene and send in commandos and bring these girls back. . . I wish that were the case, he said."
"History suggests this could be turn out to be a long affair."
British commandos joined Nigerian forces on a failed rescue operation in March 2012 in the northern city of Sokoto in which two hostages, a Briton and an Italian, were killed by their captors.