French President Francois Hollande has warned that EU sanctions on Russia could be strengthened if there is no progress at talks in Geneva on the Ukraine crisis.

"We could raise the level of sanctions if no solution emerges in Geneva, but that is not our desire," Hollande said at a joint press conference with Czech Prime Minister Bohuslav Sobotka in Paris.

He said the way out of the crisis was to "respect the political agenda" set in Ukraine, including for the presidential election on 25 May.

"This election must also be able to take place across the country and under conditions of transparency and total freedom," Hollande said.

The French president said a strengthening of sanctions against Russia could be decided during a European summit in Brussels next week.