Secretary-General Antonio Guterres on Sunday issued a "red alert" for more unity in 2018 after what he called a year of setbacks.

Nationalism and xenophobia are on the rise, inequality is growing, climate change is accelerating and the world is seeing horrific violations of human rights, he said. Global anxieties about nuclear weapons were the highest since the Cold War.

The Portuguese diplomat made no mention of specific countries in his brief New Year's message.

Guterres said he took office a year ago with an appeal that 2017 would be a year of peace

"Unfortunately — in fundamental ways, the world has gone in reverse," he said. "On New Year's Day 2018, I am not issuing an appeal. I am issuing an alert — a red alert for our world."

Guterres was the UN High Commissioner for Refugees from 2005 to 2015. During his first year in office, he has contended with humanitarian crises in Myanmar, Yemen, Syria and elsewhere.