Surprised by the speed at which sanctions have been poured on Russia, Biden’s top aides suspect that Putin’s reaction will be to double down and lash out — and perhaps expand the war.

WASHINGTON — Senior White House officials designing the strategy to confront Russia have begun quietly debating a new concern: that the avalanche of sanctions directed at Moscow, which have gained speed faster than they imagined, is cornering President Vladimir V. Putin and may prompt him to lash out, perhaps expanding the conflict beyond Ukraine.

In Situation Room meetings in recent days, the issue has come up repeatedly, according to three officials. Mr. Putin’s tendency, American intelligence officials have told the White House and Congress, is to double down when he feels trapped by his own overreach. So they have described a series of possible reactions, ranging from indiscriminate shelling of Ukrainian cities to compensate for the early mistakes made by his invading force, to cyberattacks directed at the American financial system, to more nuclear threats and perhaps moves to take the war beyond Ukraine’s borders.

The debate over Mr. Putin’s next moves is linked to an urgent re-examination by intelligence agencies of the Russian leader’s mental state, and whether his ambitions and appetite for risk have been altered by two years of Covid isolation.

Those concerns accelerated after Mr. Putin’s order on Sunday to place the country’s strategic nuclear weapons on a “combat ready” alert to respond to the West’s “aggressive comments.” (In the ensuing days, however, national security officials say they have seen little evidence on the ground that Russia’s nuclear forces have actually moved to a different state of readiness.)

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MORE FROM THE NEW YORK TIMES:

• What does Russia want in Ukraine? Explore the causes of the conflict and the history of the relationship between the two countries.

• Russia’s attack was preceded by months of military buildup on the border with Ukraine and rising tensions. Here is how the invasion unfolded.

• The fate of Ukraine could have enormous implications for the world. Learn more about what’s at stake.