U.S. President Joe Biden warned Thursday that Russia could still invade Ukraine within days and Russia expelled the No. 2 diplomat at the U.S. Embassy in Moscow, as tensions flared anew in the worst East-West standoff in decades.

NATO allies accused Russia of misleading the world by saying it was returning some troops to bases but instead moved in thousands of new ones. The pullout pledge was among Russian gestures this week that briefly cooled temperatures. Russia is believed to have some 1,50,000 military forces around Ukraine’s borders, raising fears of a new war in Europe. Tensions also spiked Thursday along the line that separates Ukrainian forces from Russia-backed separatists, with each accusing the  other of intensive shelling.