German Foreign Minister Frank-Walter Steinmeier welcomed Thursday Vladimir Putin's "constructive tone" on Ukraine, after the Russian president told rebels to halt plans for independence votes and said his troops have pulled back from the border.

"I welcome the constructive tone that President Putin used after his meeting with the OSCE president Didier Burkhalter," Steinmeier said in a statement, calling for "what was discussed in Moscow" to be implemented immediately.

"The situation is critical, but there is still a chance that we can avoid a fresh escalation in violence and the total loss of control in eastern Ukraine by diplomatic means," he said.

Pro-Russian rebels in Ukraine are due to decide Thursday whether to agree to delay independence referendums planned for Sunday.