President Biden is urging U.S. citizens in Ukraine to leave immediately, saying he would not send troops to rescue them in the event of a Russian invasion.

President Joe Biden: “That’s a world war when Americans and Russians start shooting at one another.”

Russia has denied it plans to invade Ukraine, but tensions remain high as the involved parties are at a stalemate over Russian demands NATO halt its eastward expansion. As Russia, the U.S. and NATO countries have been beefing up their military presence in Eastern Europe, progressive Democrats in the U.S. are calling for a diplomatic resolution to the crisis. On Thursday, Bernie Sanders spoke on the Senate floor.

Sen. Bernie Sanders: “No one knows exactly what the human costs of such a war would be. There are estimates, however, that come from our own military and intelligence community that there could be over 50,000 civilian casualties in Ukraine, not to mention millions of refugees flooding neighboring countries as they flee what could be the worst European conflict since World War II.”

Meanwhile, the outlet Sludge reports some lawmakers are rushing to increase their stock in energy companies as the U.S. ramps up exports of liquid natural gas to Europe, in case Russia cuts off its supply.