Russian President Vladimir Putin called on Kiev to immediately cease hostilities and return to the negotiating table.
"We call on the Kiev regime to immediately cease fire, all hostilities, to stop the war that Kiev started back in 2014, and to return back to the negotiating table," Putin said, speaking during the ceremony of signing of treaties on accession of four new territories.
Putin noted that Russia repeatedly stated its readiness for negotiations.
According to AFP, Putin staged a grand ceremony in Moscow on Friday to celebrate the annexation of four parts of Ukraine occupied by his army.
Putin was defiant during his address to Russia's political elite, telling the West that the internationally condemned manoeuvre was irreversible and urging Ukraine to negotiate a surrender.
"I want to say this to the Kyiv regime and its masters in the West: People living in Lugansk, Donetsk, Kherson and Zaporizhzhia are becoming our citizens forever," Putin said.
The packed hall erupted into chants of "Russia! Russia" after the deal was inked.
Putin -- rarely seen making physical contact since the pandemic -- joined hands with his proxy leaders from the annexed regions and they shouted along in unison on state TV.
Washington announced "severe" new sanctions against Russian officials and the country's defence industry, and said G7 allies support imposing "costs" on any nation that backs the annexation.
NATO chief Jens Stoltenberg slammed the annexation as "illegal and illegitimate" but remained non-committal after Ukraine said it was applying to join the Western alliance.
The United States and Canada voiced support for Ukraine's membership but steered clear of promises to fast-track it.
US National Security Advisor Jake Sullivan said Friday that Washington would announce an "immediate" new weapons shipment for Kyiv next week.
Sullivan also said that while there is a "risk" of Putin using nuclear weapons, there is no indication that he would imminently do so.
