By Stephanie Busari, CNN

(CNN) -- Nigeria is negotiating for the release of schoolgirls abducted last month from the town of Dapchi rather than taking military action, President Muhammadu Buhari said.

"We are trying to be careful. It is better to get our daughters back alive," Buhari said in a statement.

Boko Haram kidnapped 110 girls February 19 from Dapchi in Nigeria's Yobe state after the militants raided their school.

Buhari added that Nigeria was working with international organizations and negotiators to ensure the girls were released unharmed, including those who were also abducted from Chibok in Borno state in 2014.

In April of that year, Boko Haram sparked international outrage when the militants captured 276 girls -- between the ages of 16 and 18 -- from a boarding school in Chibok. One-hundred three of the girls have been freed in two swaps with Boko Haram. But more than 100 of the girls remain in captivity, their whereabouts unknown.

Buhari is due to visit Yobe state this week as part of a "condolence and sympathy visits to (an) area where we have had unfortunate events," he said.

Buhari made the statement as he received US Secretary of State Rex Tillerson on Monday in Abuja shortly before the latter's ouster. (President Donald Trump announced Tuesday that he is replacing Tillerson with CIA Director Mike Pompeo.)

The Nigerian leader promised that his administration would continue to keep his citizens safe.

He also thanked the United States for its help in fighting the Boko Haram insurgency but called for more assistance in the areas of training and equipment, Buhari aide Femi Adesina said in a statement.

Buhari pledged free and fair elections in 2019. Recalling a visit from a previous secretary of state before the 2015 elections, he said that John Kerry "told the party in government then, and those of us in opposition, to behave ourselves, and we did."