US President Joe Biden will hold a secure call with allies and partners on Monday to discuss "developments" in Russia's attack on Ukraine and "coordinate our united response," the White House said.
The administration did not elaborate on who would participate in the call, which will take place at 9.45 pm.
Russia has become an international pariah as its forces do battle on the streets of Ukraine's cities, and is facing a barrage of sanctions, including a ban from Western airspace and key financial networks.
Earlier Sunday, the G7 threatened fresh sanctions as top US diplomat Antony Blinken said the group of wealthy nations was "fully aligned" against Moscow's invasion of Ukraine.
Also on Sunday, Russian President Vladimir Putin ordered that Russia's nuclear "deterrence forces" be put on high alert, prompting an immediate international outcry, with the United States slamming the order as "totally unacceptable."
Biden's call with allies will come as the UN General Assembly debates a resolution condemning Russia's invasion of its neighbour.
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