Pakistani rights activist Malala Yousafzai has met Nigeria's President Goodluck Jonathan to press for more action to free at least 200 girls held by Boko Haram Islamist militants.
The militants' leader has reiterated in a new video message that he is prepared to negotiate a prisoner swap for them.
He also expressed support for Abu Bakr al-Baghdadi, the self-declared caliph of a new Middle Eastern state.
Boko Haram sparked a global outcry when it abducted the girls three months ago.
Mr Jonathan's government has faced strong criticism for not doing enough to curb violence by Boko Haram, especially in the wake of the kidnappings.
Malala met Mr Jonathan in the Nigerian capital, Abuja, and urged him to meet the families of the kidnapped girls.
She met relatives of the girls on Sunday, and expressed solidarity with them.
BBC Nigeria correspondent Tomi Oladipo says it is highly unusual that the president has not spoken to the relatives, exactly three months after the abductions.
The military has also failed to debrief some of the girls who managed to escape from captivity, he says.
But in a statement after his meeting with Malala, President Jonathan said he would meet with the parents before they left Abuja "to personally comfort them and reassure them" that the government was doing "all within its powers to rescue their daughters".
The notion that the government has not been doing enough to find and rescue the girls was "very wrong and misplaced", the statement said.
"Terror is relatively new here and dealing with it has its challenges. The great challenge in rescuing the Chibok girls is the need to ensure that they are rescued alive," Mr Jonathan said.
After meeting the parents, Malala said she understood their suffering.
"It's quite difficult for a parent to know that their daughter is in great danger. My birthday wish this year is... bring back our girls now, and alive."
Two years ago, Malala was shot in the head by Pakistani Taliban militants for campaigning for girls' education.
She survived after being airlifted to the UK for treatment.
On Sunday, Boko Haram's leader Abubakar Shekau released a video mocking the "Bring Back Our Girls" social media campaign pressing for the release of the more than 200 girls it is holding captive.
Underlining Boko Haram's offer for a prisoner swap, he promoted his own slogan: "Bring Back Our Army".
In the video Mr Shekau described several of the world's most prominent militant Islamists as his "brethren".
They included Mr Baghdadi, who claims to head a new Islamic state in Syria and Iraq, Ayman al-Zawahiri, the leader of al-Qaeda, and Mullah Omar, the head of the Afghan Taliban.
He also said that Boko Haram was behind several recent attacks, including the bombing of a shopping centre in Abuja which killed at least 21 people.
Boko Haram, which means "Western education is forbidden" in the regional Hausa language, launched an insurgency in Nigeria in 2009 to create an Islamic state.
The group took the girls hostage during a raid on their boarding school in the north-eastern town of Chibok in Borno state on 14 April 2014.
The government has rejected Boko Haram's proposal to release the girls in exchange for its fighters and their relatives who are currently in prison.
Who are Boko Haram?
- Founded in 2002
- Initially focused on opposing Western education - Boko Haram means "Western education is forbidden" in the Hausa language
- Launched military operations in 2009 to create Islamic state
- Thousands killed, mostly in north-eastern Nigeria - also attacked police and UN headquarters in capital, Abuja
- Some three million people affected
- Declared terrorist group by US in 2013