A ceasefire will begin in eastern Ukraine on 15 February, the leaders of Russia and Ukraine have announced.
"We have managed to agree on the main issues," Russia's Vladimir Putin said after marathon talks with Ukraine's Petro Poroshenko, as well the leaders of France and Germany.
French President Francois Hollande said a "serious deal" had been reached, although work remained to be done.
Thousands of people have been killed in the fighting in the east of Ukraine.
The meeting in Belarus - which lasted for about 17 hours - was focused on securing a ceasefire, withdrawal of heavy weapons and creating a demilitarised zone in Eastern Ukraine.
Mr Putin said the agreement also established a line from which heavy weaponry would be pulled back. Ukraine's pro-Russian rebels have accepted the deal, the leaders said.
Mr Hollande said he and German Chancellor Angela Merkel would ask their European Union partners to support it at a summit later in the day.