Vatican spokesman the Rev Federico Lombardi said their talks concentrated on the Ukraine conflict and the Middle East, where the Holy See is worried about the fate of the Christian minority.

Putin earlier today met Italian Prime Minister Matteo Renzi in Milan and arrived an hour late to the meeting at the Vatican, his second with Francis since he became Pope in 2013.

Lombardi said Francis stressed the need "to commit oneself in a sincere and great effort to bring" peace to Ukraine, through dialogue and implementation of the Minsk accords.

Francis also urged access for humanitarian aid. The United States, using diplomatic channels, had encouraged the Vatican to use the private papal audience as an occasion to join the West in condemning Moscow's actions in Ukraine.

The US ambassador to the Holy See, Kenneth Hackett, said the US would like to see the Vatican increase its concern about what is happening in Ukraine during the pope's meeting with Putin.

"We think they could say something more about concern of territorial integrity, those types of issues," said Hackett. "It does seem that Russia is supporting the insurgents. And it does seem that there are Russian troops inside Ukraine. This is a very serious situation."

Earlier today, however, Putin won lavish praise from Renzi as a crucial player in international anti-terrorism efforts, as Renzi sought the Russian president's help in ending the conflict in Libya that has fueled the Mediterranean migrant crisis.

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