At a summit in Brussels, Group of Seven (G7) leaders warned President Vladimir Putin that he "must stop" Russia's "destabilizing" actions in Ukraine or face further sanctions.
At the close of the two-day summit earlier on June 5, European Commission President Jose Manuel Barroso said, "The G7 stands united behind Ukraine, politically and economically."
"The G7 leaders will convey this message" to Putin on the sidelines of D-Day commemorations in France on June 6, he added.
The G7 meeting was originally supposed to take place in Sochi, Russia, but the summit was moved to Brussels after Russia annexed Crimea in March.
Later on June 5, Obama flew to Paris for talks with French President Francois Hollande, who is also scheduled to meet separately with Putin in the evening.
Hollande planned a second dinner with Putin at the Elysee Palace so the U.S. and Russian presidents would not sit at the same table.
Meanwhile, Cameron met with Putin at the French capital's Charles de Gaulle airport.
After the talks, the British prime minister said he had given the Russian president a "very clear and firm set of messages."
"The status quo, the situation today, is not acceptable and it needs to change," he added.
The Russian president is also scheduled to hold talks with German Chancellor Angela Merkel in France ahead of the D-Day anniversary.
WATCH: Obama urges Russia to engage Ukraine.
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The Kremlin has said no one-on-one meeting with Obama is planned, but in an interview with French radio, Putin suggested he is open to meetings with both Obama and Poroshenko.
It is Putin's first Western trip since the annexation of Crimea.
