The UN Secretary-General Antonio Guterres told reporters that if Russia moves ahead with its plans to annex four Ukrainian regions, it would be a dangerous escalation and would jeopardise the prospects for peace in the region.
Russian President Vladimir Putin is expected to sign documents on Friday proclaiming Russia's annexation of four Ukrainian regions, as Moscow rushes to lock in territorial claims that the Ukrainian army is threatening to reverse on the battlefield.
The move, one of the legal steps Russia says will lead to the annexation of 15 per cent of Ukraine's territory, confirms that Putin is pressing ahead with his war against Ukraine despite suffering a major military reversal this month.
The annexation, after what Western countries and Kyiv say were phony referendums staged at gunpoint on Russian-held Ukrainian territory, has been rejected by the West as an illegal seizure of land captured in war.
Any decision by Russia to go forwards will jeopardise the prospects for peace, Guterres said.
It will affect the global economy, especially in developing countries, and hinder our ability to deliver life-saving aid across Ukraine and beyond.