06/11/2015 07:20 EDT | Updated 06/11/2016 05:59 EDT

Pope Francis, Canadian PM Stephen Harper meet at Vatican

Stephen Harper and his wife Laureen met with Pope Francis today at the Vatican, although it wasn't immediately known what Canada's prime minister and the head of the Roman Catholic Church discussed.

Harper was expected to raise the issue of Russian aggression in Ukraine, a day after Pope Francis met with Russian President Vladimir Putin, also at the Vatican.

Harper had also been planning to invite Francis to Canada for Canada's 150th birthday celebrations in 2017.

It was expected that the Pope would bring up the top of climate change, as he has raised the topic of environmental issues with several world leaders recently.

On June 18, Francis will release one of his occasional "encyclicals" – a letter to one billion Catholics worldwide – with a focus on stewardship of the environment.