The activist said Boko Haram's current offer is limited to the girls from the school in northeastern Nigeria whose mass abduction in April 2014 ignited worldwide outrage and a campaign to "Bring Back Our Girls" that stretched to the White House.
The new initiative reopens an offer made last year to the government of former President Goodluck Jonathan to release the 219 students in exchange for 16 Boko Haram detainees, the activist said.
Fred Eno, an apolitical Nigerian who has been negotiating with Boko Haram for more than a year, told the AP that "another window of opportunity opened" in the last few days, though he could not discuss details.
He said the recent slew of Boko Haram bloodletting -- some 350 people killed in the past nine days -- is consistent with past ratcheting up of violence as the militants seek a stronger negotiating position.
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"Most wars, however furious or vicious, often end around the negotiation table," he said.
Eno said the 5-week-old administration of President Muhammadu Buhari offers "a clean slate" to bring the militants back to negotiations that had become poisoned by the different security agencies and their advice to Jonathan.
Two months of talks last year led government representatives and Eno to travel in September to a northeastern town where the prisoner exchange was to take place, only to be stymied by the Department for State Service intelligence agency, the activist said.
It is not known how many Boko Haram suspects are detained by Nigeria's intelligence agency, whose chief Buhari fired last week.
The activist said the agency continues to hold suspects illegally because it does not have enough evidence for a conviction, and any court would free them.
Nigerian law requires charges be brought after 48 hours.