German Chancellor Angela Merkel says Russian President Vladimir Putin must send more "signals of de-escalation" to help calm the situation in Ukraine and make presidential elections there possible on May 25.

Merkel spoke Saturday after meeting French President Francois Hollande in her constituency in northeastern Germany. The two leaders stressed their view that a sovereignty referendum planned Sunday by pro-Russian insurgents in two troubled eastern Ukrainian regions is illegitimate.

The rebels are going ahead with the referendum despite Putin's call on Wednesday to delay the vote.

Merkel said: "The Russian president must send more signals of de-escalation" so the presidential elections can go ahead.

Merkel said she would like to see a "national dialogue" in Ukraine start next week if possible, but didn't specify who should participate.