Nagy, the Assistant Secretary of State for the Bureau of African Affairs made the call during a telephonic press briefing from Kigali, Rwanda.
He argued that only dialogue, not bloodshed, can end the Cameroonian crisis.
“My heart breaks for Cameroon … I just don’t understand why this crisis goes on and on and on,” he told reporters.
Cameroon has been embroiled in a bloody battle between armed separatists demanding independence, and soldiers, vowing not to let Cameroon break up.
Hundreds have died, thousands of Anglophones have been displaced to Nigeria while schools have been burned to ashes and several people have been kidnapped.
President Paul Biya of Cameroon, who has been in power for close to four decades, has described the armed secessionists as terrorists, and vowed never to negotiate with armed groups that take up weapons against a sovereign nation like Cameroon.
Anglophones have argued that in a country where they are treated as second class citizens, only independence would bring about true peace.
They have also argued that with soldiers killing their people and reportedly burning villages, they had no choice but to arm themselves.
Authorities have countered the violence claim argument, saying that the armed activists, who are reportedly sponsored from Maryland in the United States, were burning schools and abducting students to curry sympathy from donors and nations around the world.
Secretary Nagy, who is on his third African tour since he was sworn into office late last year, would be in Cameroon in a few days.
He addressed other hot topics on the continent during his briefing meant to preview Deputy Secretary of State John Sullivan’s trips to South Africa and Angola this week and next.
Giving sometimes vague answers to concrete questions, and dropping public relations lines, the diplomat failed the clarify President Trump’s new US Africa policy, only repeating that Secretary Sullivan would be promoting trade ties in South Africa and Angola.
He did not mention China, nor the electoral hacking threat reportedly posed by Russia or abuse of privacy in Africa from social media networks such as Facebook and Twitter.