It would be “catastrophic” if the Russia-Ukraine crisis escalated into a war, UN chief Antonio Guterres told the opening ceremony of the Munich Security Conference on Friday, which Moscow is not attending this year.

“With a concentration of Russian troops around Ukraine, I am deeply concerned about heightened tensions and increased speculation about a military conflict in Europe,” Guterres said. If that happened, “it would be catastrophic,” he warned. “There is no alternative to diplomacy.”