Experts are concerned that President Joe Biden's plan to shore up Europe's supply of natural gas if Vladimir Putin cuts off supplies won't work

It's unclear how other nations and companies can make up the shortfall

Qatar, the world's third-largest producer of natural gas, is operating at capacity and has to meet its contracts with Asian customers

White House downplayed concerns, saying they are looking at range of options

White House also argues Putin won't cut off the revenue stream Russia gets from natural gas at a time the industry is seeing record profits 

Compounding the problem: European gas reserves are at record lows 

The Biden administration is preparing contingency plans in case Russia cuts off its energy exports to Europe in the event of an invasion of the Ukraine  

U.S. is working with energy producers in Middle East, Asia and North Africa to ensure Europe has enough supplies in case Russia cuts off availability 

European allies are worried that Putin would cut off their supply chain in retalation for any economic sanctions the U.S. has vowed

U.S. promising harsh sanctions if Russian invades Ukraine 

'The gradualism of the past is out. And this time, we'll start at the top of the escalation ladder and stay there,' a senior administration official said