The last pope to visit was Pope John Paul II during a tour of Central America in 1983.
A massive power outage hit Panama on Sunday, three days before the arrival of Pope Francis for a World Youth Day festival, authorities said.
The electric power company ETESA said service to various parts of the country had been affected by "an event in the integrated national system."
"Teams are working to re-establish service as soon as possible," the company said on Twitter.
ETESA, which gave no details on the cause of the outage, said power would be restored gradually.
Pope Francis is scheduled to visit Panama from Wednesday until Sunday, January 27 for the World Youth Day festival, which is expected to draw at least 200,000 people.
It would be the 26th foreign trip by the Argentine-born pope since he was chosen to lead the Catholic Church in early 2013 -- and the first to Panama.