The United Nations Security Council on Monday will hold a meeting to discuss the deteriorating humanitarian situation in Ukraine after more than 1.7 million Ukrainians have so far crossed into central Europe.
The meeting was expected to start at 2000GMT, three diplomats said.
The United Nations has been at the forefront of diplomatic efforts urging an end to Russia's invasion of Ukraine.
Russia has called the campaign it launched on February 24 a "special military operation".
France and Mexico last week worked on a resolution to the UN Security Council to address the humanitarian impact, but it was unclear if it would be formally tabled on Monday's meeting.
A total of 1,735,068 civilians - mostly women and children, as men stayed home to fight - have crossed the border into central Europe, the UNHCR said.
Poland, which has the largest Ukrainian community in the region - has received more than 1 million Ukrainian refugees, with the milestone passed late on Sunday.


Chinese national rescued from Nepal tunnel 10 days after flash flood
US envoys Witkoff, Kushner arrive in Moscow for talks on peace in Ukraine
One dead, 11 people missing after mudslide in China's Jiangxi province
Philippine VP Duterte posts bail after arrest order for alleged grave threats
Lindsay Clancy trial over killing her children ends in mistrial
Israel says it strikes southern Lebanon after Hezbollah drone launch
Sydney sweats in spring hot spell, faces 'extreme' bushfire risk
Nine days after disaster, two pulled alive from Nepal hydropower tunnel
