Obama calls on Putin to meet Ukraine's Poroshenko

US President Barack Obama today called on Russia's President Vladimir Putin to meet the next leader of Ukraine, Petro Poroshenko.

Obama said that he would give that message to Putin when he sees him this week in France for D-Day 70th anniversary celebrations, and called on the Russian leader to recognise the Ukrainian election as "legitimate".

Obama noted that he will meet with president-elect Poroshenko in Warsaw tomorrow and would be interested to see what approach to Russia by the United States would be "helpful" to the Kiev government.

The US leader said Putin could "meet with the president-elect of Ukraine, recognise that was a legitimate election and help to facilitate the kind of dialogue along the Ukraine-Russia border that will calm the situation down," Obama said.

The US leader said that if Putin was constructive it would be possible to rebuild trust between Washington and Moscow that has frayed over the Ukraine crisis - but did not hold out much hope for an immediate improvement in relations.

"It is fair to say that rebuilding that trust will take quite some time," Obama said.