UN Secretary General Antonio Guterres expressed deep concern Monday over rising global discord and called for "maximum restraint" amid escalating tensions between Washington and Tehran after the United States killed an Iranian military commander.

"The New Year has begun with our world in turmoil," Guterres said in brief remarks at the UN headquarters in New York.

"We are living in dangerous times. Geopolitical tensions are at their highest level this century. And this turbulence is escalating."

Guterres did not explicitly mention the rising tensions in the Middle East following the US killing of Qasem Soleimani, head of Iran's Middle East operations, in a drone strike.

But his remarks appeared aimed, at least in part, at the two sides.

"This cauldron of tensions is leading more and more countries to take unpredicted decisions with unpredictable consequences and a profound risk of miscalculation," Guterres said.

He added that he had been following the recent rise in global tensions with "great concern" and was in constant contact with leading officials around the world.

UN Secretary General Antonio Guterres's remarks appeared aimed, at least in part, at Washington and Tehran
UN Secretary General Antonio Guterres's remarks appeared aimed, at least in part, at Washington and Tehran AFP / CRISTINA QUICLER

"And my message is simple and clear: Stop escalation. Exercise maximum restraint. Re-start dialogue. Renew international cooperation," he said.

"Let us not forget the terrible human suffering caused by war. As always, ordinary people pay the highest price. It is our common duty to avoid it."

Reacting to the US airstrike on Friday, a spokesman for Guterres said the secretary-general had "consistently advocated for de-escalation in the Gulf."

"This is a moment in which leaders must exercise maximum restraint," the spokesman said. "The world cannot afford another war in the Gulf."

The United States on Friday killed Qasem Soleimani, the commander of the Iranian Quds Force, in a drone strike on Baghdad's international airport.

Iran vowed "severe revenge" for Soleimani's death while US President Donald Trump said there would be "major" US retaliation if Tehran hits back.

US Secretary of State Mike Pompeo spoke with Guterres on Monday, the State Department said, to discuss the Middle East and Venezuela, where opposition leader Juan Guaido was re-elected national assembly speaker on Sunday in a hotly disputed vote.

Pompeo voiced his appreciation for Guterres's "continued diplomatic efforts," spokeswoman Morgan Ortagus said.