Nigeria's President Goodluck Jonathan has ruled out the release of Boko Haram fighters in exchange for the freedom of more than 200 schoolgirls kidnapped by the militants a month ago.

Britain’s Africa minister Mark Simmonds, in Nigeria for talks about the international rescue mission, told reporters Wednesday that he raised the issue with Jonathan during a meeting in Abuja.

“I did discuss this with the president and he made it very clear that there will be no negotiation with Boko Haram that involves a swap of abducted schoolgirls for prisoners”, he told reporters.

Boko Haram leader Abubakar Shekau suggested in a video released on Monday that he may be prepared to release the girls if Nigeria freed militants held in the country’s jails.

Interior Minister Abba Moro immediately rejected the plan, telling AFP that the Islamist group, which has waged a deadly insurgency in northeast Nigeria since 2009, could not dictate terms.

A door appeared to have opened to discussions about the girls on Tuesday, when special duties minister Taminu Turaki indicated that the teenagers’ freedom could up for discussion.

Simmonds said Jonathan had now ruled that out, he added that the president was still prepared to fulfil his pledge of talking to the extremists about wider issues to end the violence.

The rejection of a prisoner swap came as international powers ramped up the search effort, including with the use of US military surveillance drones and manned aircraft.

The Pentagon said it had deployed the robotic Global Hawk, which flies at high altitude, and the manned MC-12, a propeller plane heavily used in Afghanistan.

Both types of aircraft are “unarmed” and strictly being used for surveillance.

However, the data is not yet being shared with the Nigerians because Washington is still working out an agreement to govern the sharing of intelligence, Colonel Steven Warren told reporters