Russian President Vladimir Putin kept Pope Francis waiting for more than an hour for talks at the Vatican, a rare breach of protocol for world leaders meeting with the pontiff.

According to The Associated Press, Putin arrived an hour and 20 minutes late having made a stop at the world's fair to see the Russian pavilion and taking time for a meeting with Italian Prime Minister Matteo Renzi.

The issue of Ukraine was raised during the brief, closed-door meeting. Afterward, the Vatican issued a statement saying "The Holy Father affirmed that it is necessary to make a sincere and great effort to forge peace," CNN reported.

But some feel the Pope has not taken a strong enough stand on the issue of Russia's involvement in the Ukraine conflict.

Earlier in the day, the U.S. ambassador to the Holy See, Kenneth Hackett, said the United States would like to see the Pope voice greater concern about Russia's aggression in Ukraine.

"We think they could say something more about concern of territorial integrity, those types of issues," Hackett told reporters, according to The Associated Press. "It does seem that Russia is supporting the insurgents. And it does seem that there are Russian troops inside Ukraine."

The meeting came just a day after the U.S. and the G7 threatened Russia with more sanctions in the event that the situation in the Ukraine worsened.

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