Fears that Russia could invade Ukraine grew more concrete on Friday as the US issued a warning that such an attack could conceivably come within the next 10 days, while Western governments urged their citizens to get out of Ukraine. Speaking to reporters after US President Joe Biden conducted a videoconference with multiple world leaders, US National Security Advisor Jake Sullivan said there are new concerns that the long-feared attack could start before the Winter Olympics end on February 20. Until now, most speculation of any such attack had leaned towards an invasion starting after the Olym…