WASHINGTON (AP) — How do American leaders and their allies intend to respond if President Vladimir Putin seeks to escalate his way out of a bad situation on Ukraine’s battlefields, and makes good on renewed threats of annexing territory or even using nuclear weapons?

It’s been tough enough staying the current course of persuading all of dozens of allies to stick with sanctions and isolation for Putin, and persuading more ambivalent countries to join in.

or NATO officials matching Putin’s renewed nuclear threats with the same nuclear bluster, which in itself might raise the risks of escalating the conflict to an unimaginable level.

Even if Putin should act on his nuclear threat, President Joe Biden and others point, without details, to an ascending scale of carefully calibrated responses, based on how far Russia goes.

“I do not believe the United States would take an escalatory step” in the event of a one-off, limited nuclear detonation by Russia aimed at trying to scare Ukraine and its supporters off, said Rose Gottemoeller, former deputy NATO secretary-general and former U.S.

Beyond the economic sanctions, the EU since Russia’s February invasion of Ukraine has slapped asset freezes and travel bans on more than 1,200 Russians, including Putin, Russia’s foreign minister and other senior officials.

as a matter of policy maintains ambiguity about how it would respond to any use of nuclear weapons in the conflict.

A one-off and comparatively limited Russian nuclear use would deepen Russia’s isolation internationally, but may not necessarily draw an immediate Western nuclear use in kind.

It’s difficult to fathom Putin launching any central strategic nuclear strike at the United States or its NATO allies, which would be “to commit suicide,” said Gottemoeller, the former deputy NATO secretary-general.

For Putin, actual nuclear use would give up all the benefits of simply threatening it, and pile on untold risks for Putin after that, said Lawrence Freedman, emeritus professor of war studies at King’s College London.

“To start using nuclear weapons against the West, you have to expect” at least the risk of “nuclear weapons coming back in your direction.”