The most punitive sanctions that US officials have threatened to impose on Russia could cause severe inflation, a stock market crash, and other forms of financial panic for Russia. People in the country - from billionaires, government officials to middle-class families, are worried. US officials vow to launch swift economic actions if Russia invades Ukraine, including sanctions on its biggest banks and financial institutions, in a way that is certain to affect everyday life. But strategy involves political and economic risks. No country has ever attempted to impose such broad-based sanctions on such important financial institutions and against an economy of its size. The "quick and stern" response promised by US officials  could affect major economies, especially in Europe, and even threaten the stability of the US, analysts say. 

Some analysts also warn of a potential spiral of escalation. Russia could retaliate for the economic  punch by cutting off natural gas shipments to Europe or staging cyberattacks on US and European infrastructure. The pain of sanctions could stoke public anger towards Russian President Vladimir V. Putin. But history shows that the country doesn't give up easily, and resilience is an important part of its national identity. American officials are also sensitive to the idea that they could be seen as punishing the Russian people - a perception that could fuel anti-Americanism and Mr. Putin's narrative that his country is under siege.

From Cuba to North Korea to Iran, US sanctions have a mixed track record  of forcing behavior change at best. And while the Biden administration and its European allies try to deter Mr. Putin with harsh words, some experts wonder if they will follow through with the most drastic economic measures, should the Russian military cross the border. 

President Biden said he would not send US troops to defend Ukraine. Instead, US officials are trying to devise a punitive response that could deal a  blow to Russia while limiting economic shocks around the world, including in the United States. Officials say the Biden administration currently has no plans to target Russia's huge oil and gas export industry; it could raise gas prices for Americans already struggling with inflation and create a divide with European allies.

But many sanctions experts say that the toughest sanctions on Russia's financial sector, if passed, could have significant consequences.