Russia has said on that peace talks with Ukraine had not progressed enough for a leaders' meeting and that Moscow's position on the status of Crimea and Donbas remained unchanged.
"The draft agreement is not ready for submission to a meeting at the top," Russian chief negotiator Vladimir Medinsky said on Telegram. "I repeat again and again: Russia's position on Crimea and Donbas remains unchanged."
The two sides have held periodic talks since Russia launched its invasion on February 24 but there has been no breakthrough and they remain far apart on the question of territory.
Medinsky said that Ukraine had started to show a more realistic approach to peace talks.
He said Ukraine had agreed it would be neutral, not have nuclear weapons, not join a military bloc and refuse to host military bases.
On the questions of Crimea, which Russia annexed from Ukraine in 2014, and two Russian-backed rebel regions in the eastern Donbas that President Vladimir Putin recognised as independent in February, however, Medinsky indicated there had been no progress.
Medinsky said he did not share the optimism of Ukrainian negotiator David Arakhamia, who told Ukrainian television on Saturday that the draft deal was advanced enough to allow consultations between Putin and Ukrainian President Volodymyr Zelenskiy.
"Unfortunately, I don't share Arakhamia's optimism," Medinsky said. "Moreover, Ukrainian diplomatic and military experts lag far behind on confirming even those agreements which were already reached at the political level on the draft text."
Talks via videoconference would continue on Monday, he said.
Putin has said the "special military operation" in Ukraine is necessary because the United States was using Ukraine to threaten Russia and Moscow had to defend against the persecution of Russian-speaking people by Ukraine.
Ukraine has dismissed Putin's claims of persecution and says it is fighting an unprovoked war of aggression.