Obama confirmed that Nigerian leaders had accepted a US offer to deploy experts there, saying "we've already sent in a team to Nigeria," consisting of "military, law enforcement, and other agencies."
"It's a heartbreaking situation, outrageous situation," Obama told US broadcaster ABC.
But "this may be the event that helps to mobilize the entire international community to finally do something against this horrendous organization that's perpetrated such a terrible crime," he said.
The news of the US deployment came as eight more schoolgirls were kidnapped by gunmen from the village of Warabe in Nigeria's embattled northeast, near Chibok, residents said.
The first group of girls were taken three weeks ago, and concerns have been mounting about their fate after Boko Haram chief Abubakar Shekau claimed responsibility, saying his extreme Islamist group was holding the schoolgirls as "slaves" and threatening to "sell them in the market."
The American team will work to "identify where in fact these girls might be and provide them help," the US president said, denouncing Boko Haram as "one of the worst regional or local terrorist organizations."
US officials have voiced fears that the girls, aged between 16 and 18, have already been smuggled into neighboring countries, such as Chad and Cameroon.
US Secretary of State John Kerry said Tuesday he had offered US help in a phone call to Nigeria's President Goodluck Jonathan.
Washington will also set up a coordination cell at its embassy in Abuja with US military personnel, law enforcement officials as well as experts in hostage situations.
"President Goodluck Jonathan was very happy to receive this offer and ready to move on it immediately," Kerry told reporters, after talks with EU foreign policy chief Catherine Ashton.
In Abuja, Jonathan said his country's "security agencies, who were already working at full capacity to find and rescue the abducted girls, would appreciate the deployment of American counter-insurgency know-how and expertise in support of their efforts."
'Bring Back Our Girls'
Lawmakers have called on the Obama administration to do all it can to help free the girls, and a Twitter hashtag #BringBackOurGirls has gone viral.
The Nigerian government had "been disastrously slow in responding to incidents like the kidnapping of these girls," said Democratic Senate majority leader Harry Reid.
A father and grandfather, Reid said: "I can't imagine the horror of having my precious girls abducted."
"But for hundreds of families in Nigeria, my nightmare is their reality."
He was speaking as the Senate approved a resolution condemning Boko Haram.
The EU's Ashton said the girls' kidnapping was "devastating for all of us."
"These are the future of the country. They are teachers, dancers, politicians. They are scientists, they are mothers, they are women in the making who have a right to play their full part in their society," she said.
Some 200 protesters also gathered Tuesday outside the Nigerian embassy in Washington to demand the country take robust action to rescue the girls.
Chanting "bring back our girls" and "no more abuse," they called upon Jonathan to show what one speaker called the "testicular fortitude" to resolve the crisis.
"This is something that touched me... Kids of our generation do care about something and stand up for something," said Tifawni Haynes, 18, a high school student from Washington.
Jonathan's government has so far proved powerless in the hunt for the girls, but had been reluctant to accept any outside help.