The leaders of Germany and France say they oppose a referendum planned in eastern Ukraine for Sunday.
German Chancellor Angela Merkel and French President Francois Hollande met in northern Germany on Saturday and issued a statement.
It says the referendum planned by pro-Russia groups would be illegal.
The statement refers to recent fatal clashes between the groups and Ukraine's government forces.
It says all parties should refrain from violence and intimidation as well as provocative acts or statements.
The leaders also expressed concern about Ukraine's presidential election scheduled for May 25th.
Their statement says an internationally recognized ballot is essential to prevent further destabilization.
It says Germany and France are prepared to ramp up sanctions against Russia if it uses its influence to undermine the election.