Growing tensions between Moscow and Western powers have raised the prospect of new sanctions being imposed on Russia, possibly the most severe yet, if it attacks neighboring Ukraine.

U.S. Senate Democrats have unveiled a bill to impose sweeping sanctions on Russian government and military officials — including President Vladimir Putin — and banking institutions if Moscow engages in hostilities against Ukraine.

"If Russia is using its conventional military to acquire land in Ukraine, that will meet a severe economic response," a senior White House official said on Wednesday.