"This question is not being worked upon," Putin's spokesman Dmitry Peskov said Monday when asked whether the leaders would meet in France.
Pro-Western billionaire and chocolate company owner Poroshenko, who won last month's presidential election in Ukraine, is also due to attend the commemorations.
He has been trying to arrange what would be the first meeting between Putin and a Ukrainian leader since Russia's seizure of Crimea sparked the worst East-West crisis since the Cold War.
On Thursday evening, he will have dinner with French President Francois Hollande at the Elysee Palace.
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