Germany's foreign minister warned that Russian military action in Ukraine could create a new Iron Curtain in Europe.
In a statement issued Sunday, Frank-Walter Steinmeier said: "We are on an extremely dangerous path of escalating tensions. A change of course is still possible. There is still a chance of stopping Europe being split."
Steinmeier joined other European Union foreign ministers Monday in Brussels to push for high-level mediation to resolve the crisis.
Germany, France and Britain, the EU's most-powerful nations, are all advocating mediation, while not ruling out economic measures if Moscow does not cooperate.
"Crisis diplomacy is not a weakness but it will be more important than ever to not fall into the abyss of military escalation," Steinmeier told reporters on Monday.
Reuters contributed to this report.