Russian President Vladimir Putin is due to stage a form in an ornate Kremlin hall to annunciate Russia's rule over around 15% of Ukraine, the biggest annexation in Europe since the Nazi period.
The proclamation is to be followed by a celebratory pop musicale outside the Kremlin walls on Red Square.
Russia's annexation of the Russian- engaged areas of Donetsk, Luhansk, Kherson, and Zaporizhzhia has been condemned in the West and beyond.
UN chief Antonio Guterres called it a" dangerous escalation" and a violation of the United Nations' duty.
" It can still be stopped. But to stop it we've to stop that person in Russia who wants war further than life. Your lives, citizens of Russia," Ukrainian President Volodymyr Zelenskyy said in a Thursday evening address.
The Russian annexation, held after what the West denounced as phony blackballs at gunpoint in engaged home, followed weeks of defeats for Moscow's forces on the battleground in which they were routed from their positions in Ukraine's northeast.
Putin has ordered the call-up of hundreds of thousands of Russian reservists, a move that urged knockouts of thousands of Russian men to flee over borders to escape being packed off to war.