Kiev, March 14 : The US Embassy in Kiev on Monday asked American nationals in Ukraine to leave the war-torn nation as Russia continued its assault for the 19th day. Taking to Twitter, the Embassy said: "We urge US citizens to depart Ukraine now via ground transport if safe. Border crossings are open. Consider routes & risks; roads may be crowded, exposed to combat or have damaged infrastructure. "Sheltering in place may be the best option for some." In a similar notice issued on March 9, the Embassy had asked Americans to "depart Ukraine immediately" as the security situation throughout the country "continues to be violent and unpredictable due to ongoing military attacks by Russia, with active fighting in country and uncertain safety conditions" The Embassy's announcement on Monday came shortly after US Secretary of State Antony Blinken spoke to Ukrainian Foreign Minister Dymtro Kuleba. Blinken said in a tweet that they spoke about Washington's "steadfast support of Ukraine's sovereignty and territorial integrity and ongoing efforts to stop (Russian President Vladimir) Putin's war of choice". On his part, Kuleba said they both agreed that" more needs to be done to stop Russian aggression and hold Russia accountable for its crimes". He thanked the US for "firmly standing by the people of Ukraine". /IANS