German Foreign Minister Frank-Walter Steinmeier warned that the cease-fire between Ukrainian government forces and pro-Russian separatists is becoming more fragile.
"Even if the situation in eastern Ukraine has disappeared from the headlines, there is no reason to sit back... The cease-fire is increasingly fragile," he said.
Steinmeier condemned violations of the truce over the Christmas holiday and urged both sides to stick with their pledges to stop the war, at least temporarily.
Steinmeier pointed to progress in military de-escalation and the withdrawal of weapons by both sides, but said important questions remain to be resolved.
These included agreeing on a special law for local elections in parts of the east controlled by separatists and improving the humanitarian situation.
He called for the release of prisoners and hostages, a resumption of water supplies in the east, and the end of limits on the registration of aid organizations in the east.
"We must continue to work so that the local elections take place at the beginning of 2016 and the Minsk package of measures is completely implemented," he said.