US Secretary of State John Kerry was to meet with French President Francois Hollande, hours after police in neighbouring Belgium launched an anti-terrorist raid.
The meeting in Astana in Norman format (with the participation of leaders of Ukraine, Russia, Germany, France) to resolve the situation in Ukraine is at the stage of preparations.
Hollande received a warm ovation from the crowd that thronged the French capital, belying the president's standing in opinion polls that hit a record low just months ago.
Millions marched against terrorism in the largest protests France has ever seen, led by world leaders in Paris uniting in tribute to the victims of Islamist attacks.
The weapons wielded by gunmen sowing mayhem at Charlie Hebdo magazine and a Jewish supermarket in Paris this week were powerful but available in France.