The White House announced that US President Joe Biden will hold a secure call with allies and partners on Monday to discuss "developments" in Ukraine and "coordinate our united response."

The administration did not specify who would take part in the call, which will begin at 11:15 a.m. (16:15 GMT).

Earlier on Sunday, the G7 threatened new sanctions, with the US Secretary of State Antony Blinken declaring that the group of wealthy nations was "fully aligned" against Russia's invasion of Ukraine.

Also on Sunday, Russian President Vladimir Putin ordered Russia's nuclear "deterrence forces" to be placed on high alert, with the US calling the order "totally unacceptable."

Biden's call to allies comes as the United Nations General Assembly debates a resolution condemning Russia's military operation in Ukraine.

Putin stressed that Russia does not "plan to occupy Ukrainian territory," explaining that Russia's goal is to protect people who, over eight years, have been subjected to abuse and genocide by the Kiev regime.