Sokoto Sultan and President-General of the Nigerian National Supreme Council for Islamic Affairs (NSCIA) Muhammad Sa'ad Abubakar (R) speaks next to US Secretary of State John Kerry at the Palace of the Sultan in Sokoto, on August 23, 2016. Kerry congratulated Nigeria on its recent military successes against Boko Haram, but warned the country will face a blowback if it "cracks down" on the Islamists with excessive force. The top US diplomat, who was in Kenya on August 22, is expected to discuss the Boko Haram insurgency, fighting corruption and boosting Nigeria's moribund economy that has been pummelled by the drop in global oil prices. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images

US Secretary of State John Kerry stands as he delivers a speech on "the importance of resilient communities and religious tolerance in countering violent extremism'' at the Palace of the Sultan in Sokoto, on August 23, 2016. Kerry congratulated Nigeria on its recent military successes against Boko Haram, but warned the country will face a blowback if it "cracks down" on the Islamists with excessive force. The top US diplomat, who was in Kenya on August 22, is expected to discuss the Boko Haram insurgency, fighting corruption and boosting Nigeria's moribund economy that has been pummelled by the drop in global oil prices. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images

US Secretary of State John Kerry stands as he delivers a speech on "the importance of resilient communities and religious tolerance in countering violent extremism'' at the Palace of the Sultan in Sokoto, on August 23, 2016. Kerry congratulated Nigeria on its recent military successes against Boko Haram, but warned the country will face a blowback if it "cracks down" on the Islamists with excessive force. The top US diplomat, who was in Kenya on August 22, is expected to discuss the Boko Haram insurgency, fighting corruption and boosting Nigeria's moribund economy that has been pummelled by the drop in global oil prices. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images

US Secretary of State John Kerry delivers a speech on "the importance of resilient communities and religious tolerance in countering violent extremism'' at the Palace of the Sultan in Sokoto, on August 23, 2016. Kerry congratulated Nigeria on its recent military successes against Boko Haram, but warned the country will face a blowback if it "cracks down" on the Islamists with excessive force. The top US diplomat, who was in Kenya on August 22, is expected to discuss the Boko Haram insurgency, fighting corruption and boosting Nigeria's moribund economy that has been pummelled by the drop in global oil prices. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images

US Secretary of State John Kerry (L) sits next to Sokoto Sultan and President-General of the Nigerian National Supreme Council for Islamic Affairs (NSCIA) Muhammad Sa'ad Abubakar (C) and state governor Aminu Tambuwal at the Palace of the Sultan in Sokoto, on August 23, 2016. Kerry congratulated Nigeria on its recent military successes against Boko Haram, but warned the country will face a blowback if it "cracks down" on the Islamists with excessive force. The top US diplomat, who was in Kenya on August 22, is expected to discuss the Boko Haram insurgency, fighting corruption and boosting Nigeria's moribund economy that has been pummelled by the drop in global oil prices. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images

Sokoto Sultan and President-General of the Nigerian National Supreme Council for Islamic Affairs (NSCIA) Muhammad Sa'ad Abubakar (R) meets with US Secretary of State John Kerry (L) at the Palace of the Sultan in Sokoto, on August 23, 2016. Kerry ccongratulated Nigeria on its recent military successes against Boko Haram, but warned the country will face a blowback if it "cracks down" on the Islamists with excessive force. The top US diplomat, who was in Kenya on August 22, is expected to discuss the Boko Haram insurgency, fighting corruption and boosting Nigeria's moribund economy that has been pummelled by the drop in global oil prices. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images

Sokoto Sultan and President-General of the Nigerian National Supreme Council for Islamic Affairs (NSCIA) Muhammad Sa'ad Abubakar (C) flanked by US Secretary of State John Kerry (L) and state governor Aminu Tambuwal pose at the Palace of the Sultan in Sokoto, on August 23, 2016. Kerry ccongratulated Nigeria on its recent military successes against Boko Haram, but warned the country will face a blowback if it "cracks down" on the Islamists with excessive force. The top US diplomat, who was in Kenya on August 22, is expected to discuss the Boko Haram insurgency, fighting corruption and boosting Nigeria's moribund economy that has been pummelled by the drop in global oil prices. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images

United States Secretary of State John Kerry (L) talks with the Sultan of Sokoto and President-General of the Nigerian National Supreme Council for Islamic Affairs (NSCIA) Muhammadu Sa'ad Abubakar during his visit to his palace in Sokoto, on August 23, 2016. Kerry, who is on a three-nation tour is in Nigeria to discuss counterterrorism efforts, the Nigerian economy, the fight against corruption, and human rights issues. / AFP PHOTO / PIUS UTOMI EKPEIPIUS UTOMI EKPEI/AFP/Getty Images