Antonio Guterres is starting his first day as the new secretary-general of the United Nations with an appeal to all people in the world to make a New Year's resolution: "Let us resolve to put peace first."

The former Portuguese prime minister and U.N. refugee chief made the plea just after taking over the reins of the United Nations from Ban Ki-moon whose second five-year term ended at midnight on Dec. 31.

Guterres said the only way to help "the millions of people caught up in conflict, suffering massively in wars with no end in sight" is for citizens, governments and leaders to "strive to overcome our differences."

"All that we strive for as a human family — dignity and hope, progress and prosperity — depends on peace," he said.