Washington: The White House warned Friday that a major Russian assault on Ukraine, presaged by aerial bombings and missile attacks, could begin in days and told Americans there to leave within 48 hours in a dramatic elevation of the war threat level. “We continue to see signs of Russian escalation including new forces arriving at the Ukrainian border,” said National Security Advisor Jake Sullivan, warning US officials now believe Moscow may not delay an invasion — as some had suggested — until after the Winter Olympics in Beijing. “Our view that military action could occur any day now, and could occur before the end of the Olympics is only growing in terms of its robustness,” Sullivan told reporters at the White House, calling such a scenario “a very, very distinct possibility.” Sullivan stopped short of saying the United States now believes President Vladimir Putin has actually made the decision to attack. Still, the White House’s tone and language on the possibility of war in Europe were much more pointed and strident than just days ago. With more than 100,000 Russian troops and an array of military materiel amassed on the border with its pro-western neighbor, Sullivan urged Americans in Ukraine to get out quickly, while they can. “An invasion could begin at any time should Vladimir Putin decide to order it,” he said. ” “It could begin during the Olympics.” “If a Russian attack on Ukraine proceeds, it is likely, to begin with, aerial bombing and missile attacks that could obviously kill civilians,” he added. Biden has already spoken to Putin twice and warned of severe economic sanctions against Russia if it invades, and Sullivan said he expects the two leaders to speak again.