By John Irish and Jeff Mason

PARIS (Reuters) - President Francois Hollande urged world leaders arriving in France on Thursday to mark the 70th anniversary of World War Two's D-Day landings to use the occasion to ease tensions over the Ukraine crisis.

Hollande, criticised at home for a lack of initiative on Ukraine, was due to have a working dinner with U.S. President Barack Obama before dashing across Paris to join Russia's Vladimir Putin for a second evening meal later on Thursday.

One of his main aims, diplomats said, is to clear the path for an ice-breaking first meeting on French soil on Friday between Putin and Ukrainian president-elect Petro Poroshenko, even as fighting in eastern Ukraine continues between government forces and pro-Russian separatists.

The separate meals showed the lengths to which French officials have gone to keep Obama and Putin apart in Paris, at Washington's request, before Friday's commemorations of the allied D-Day landings that helped end World War Two, which will see 18 world leaders assemble on the Normandy beaches.

The French capital went into security lockdown before Britain's Queen Elizabeth arrived by train from London. She was followed by Obama, who flew in from a Group of Seven (G7) meeting in Brussels to which Putin had not been invited.

"This is an important occasion to express gratitude and fraternity, but it is also major international event which should serve the interests of peace," Hollande told the G7 summit before he too rushed back to Paris.

Asked if a Putin-Poroshenko meeting in France was possible, Hollande replied: "Yes ... I invited (Poroshenko) so he could be there, because he represents the Ukrainian people who suffered a lot during World War Two. He will be there alongside President Putin. President Putin was informed of that."

Obama called on Putin to recognise and work with Ukraine's new government and stop "provocations" along its border, or face tougher sanctions from members of the G7.

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Highlighting shades of difference among Western stances on Russia, Obama noted he would have preferred it if France had held back on the sale of Mistral helicopter carriers to Russia that Paris has insisted must go ahead.

"I recognise that this is a big deal," he told reporters. "I recognise that the jobs in France are important. I think it would have been preferable to press the pause button."

HANDSHAKE

Putin said in French media interviews on Wednesday he was open to meetings with both Poroshenko and Obama in France. While the U.S. leader has so far not taken him up on the opportunity, the two countries' foreign ministers will meet on Thursday.

Underscoring the sensitivities, Hollande will rush from meeting the Queen at his Elysee Palace to a chic restaurant overlooking the Champs-Elysees avenue to dine with Obama before returning to his residence for a late supper with Putin.

For Hollande, the Obama dinner will also be the opportunity to raise concerns about a possible $10 billion-plus U.S. fine on BNP Paribas that he considers "disproportionate". Hollande has spent much of the week trying to create a diplomatic opening on Ukraine after sending Poroshenko a last-minute invitation to the D-Day ceremonies. Ukrainians fought in the Soviet Red Army that defeated Nazi Germany.

French diplomats say Hollande, who met Poroshenko in Poland on Wednesday, wants at the very least to get Putin and the Ukrainian to shake hands at a closed-door lunch of leaders on Friday at the 18th-century Chateau de Benouville.

This, they argue, would be a tacit acknowledgement that the Russian leader recognises Poroshenko's legitimacy, the day before he is sworn in, opening the door for dialogue.

In an apparent signal of recognition, Russia's deputy foreign minister, Grigory Karasin, said Moscow's ambassador to Ukraine would attend Poroshenko's inauguration.

"We want to see Ukraine peaceful and stable for all those who live in Ukraine ... for them to feel equal, respected and listened to, living in peace, being a bridge and not a pawn," Russian Foreign Minister Sergei Lavrov told reporters in Paris before talks with U.S. counterpart John Kerry.

Putin did not rule out a first encounter with a pro-Western Ukrainian leader since Moscow's annexation of Ukraine's Crimea region in March.

"You know, I don't plan to evade anyone," Putin told TF1 television on Wednesday when asked if he was willing to meet Poroshenko. "There will be other guests, and I'm not going to avoid any of them. I will talk with all of them."

His relations with Ukraine as well as with the European Union and the United States have been strained since pro-Western protesters pushed a Moscow-friendly Ukrainian president from power in February and Russia then annexed Crimea.

Moscow has deployed tens of thousands of troops near the Ukrainian border and warned it could send them in to protect Russian-speakers. Poroshenko and Ukraine's pro-Western government have ignored Moscow's demands for an end to Kiev's military operation against the separatists.

(Additional reporting by Julien Ponthus and Roberta Rampton in Brussels, Lesley Wroughton in Paris; writing by Mark John; editing by Giles Elgood)