which way, Eastern Europe?

National Security Adviser Jake Sullivan said on Fox News Sunday that he believes Russia is prepared to invade Ukraine, Fox News reported.

“We are in the window,” Sullivan said in response to a question from host Martha MacCallum. “Any day now, Russia could take military action against Ukraine or it could be a couple of weeks from now, or Russia could choose to take the diplomatic path instead.”

President Biden told Ukrainian President Volodymyr Zelensky last month that there was a “distinct possibility” Russia could invade in February. Russian tanks and other heavy equipment will be able to move more easily over frozen ground, so if Russian President Vladimir Putin is going to order an invasion, he will need to do so before the spring thaw.

“If war breaks out,” Sullivan added, “it will come at an enormous human cost to Ukraine, but we believe … it will come at a strategic cost to Russia as well.”

Biden administration warned lawmakers last week that Ukraine could suffer 50,000 civilian casualties if Russia invades and that the capital city of Kyiv could fall to the Russians within 72 hours.

Dmitry Polyanskiy, Russia’s deputy ambassador to the United Nations, dismissed this assessment as “madness” and “scaremongering.”

Sullivan also discussed potential sanctions against Russia, which he said would include refusing to allow the Nord Stream 2 pipeline — which will transport Russian natural gas from Russia to Germany — to move forward. He said the U.S. is taking “steps to ensure that Russia’s attempts to use energy as a weapon get frustrated,” including “find[ing] cargoes of liquified natural gas going elsewhere in the world and redirect[ing] them to Europe.”

The Biden administration announced a version of this plan last month.