US urges NATO vigilance for signs Russia could use nuclear weapon in Ukraine

A general view of the NATO defence ministers' meeting at the Alliance's headquarters in Brussels, Belgium, February 14, 2023. REUTERS/Johanna Geron

WASHINGTON (Reuters) - The U.S. and its NATO allies must remain alert for signs Russian President Vladimir Putin could use a tactical nuclear weapon in a "managed" escalation of his war in Ukraine, the second-highest U.S. diplomat said on Tuesday.

Deputy Secretary of State Wendy Sherman issued the warning during the opening session of an annual NATO arms control conference that was being held in North America for the first time since its inception in 2004.