The New York Times reports:

President Biden’s national security adviser said on Sunday that the United States had warned Russia that there would be “catastrophic consequences” for the country if Moscow used nuclear weapons in its increasing desperation to hold on to territory in Ukraine, adding that in recent days the United States has “spelled out” how the world would react in private conversations with Russian officials.

The adviser, Jake Sullivan, repeated the comments several times in three Sunday television interviews, though he left deliberately vague whether those consequences would be military, economic or diplomatic. Officials were quick to say they still had not seen any movement in Russia’s stockpile of 2,000 or so small tactical weapons — which can be launched from a short- or medium-range missile — despite President Vladimir V. Putin’s threats in a televised address last week that “this is not a bluff.”

But Mr. Sullivan’s use of the word “catastrophic” as a deliberately ambiguous warning of a major — if almost certainly non-nuclear — response to a Russian nuclear detonation illustrated how quickly the rhetoric has intensified as Russia has faltered on the battlefield in recent months. [Continue reading…]