russia be effective? and how economically harmful is that to europe? >> we've already put substantial pain on russia with the enormous slew of sanctions, but there's no question that an oil and a gas embargo would dry up putin's immediate cash flow. i'm not certain that the west, especially europe, could sustain a full hydrocarbon embargo on purchases from russia, but they might be able to sustain dropping that by 30%, 40%, 50% if the united states joins that. that would cut putin's cash coming in 40%, 50%, which, again, would constrain his ability to wage war. he wouldn't stop, however, and he could stim continue this abominable campaign. >> not when it comes to russian gas and oil? >> they depend on russia for 40% of their natural gas. oil might be easier, but natural gas, not so easy.