Pope Francis has warned climate change shouldn't be left to the next generation to deal with - as he begins his first tour of the United States.

In a speech in front of the White House, the pontiff warned the world was at a 'critical moment of history'.

The Pontiff will speak to President Barack Obama on that and other issues. 

Before they began, the US President welcomed him to his country: 

Arriving in Washington Pope Francis gave a speech - saying he was delighted to be in America:

As well as climate change, the 78-year-old Pontiff is expected to address immigration during his six-day US trip.

Tomorrow he will make the first address by any pope to the US Congress and on Friday he will make a speech to the UN General Assembly in New York. He is also scheduled to deliver an open-air mass in Philadelphia. 

Pope Francis greeted by US President Barack Obama on the first day of his visit to America pic.twitter.com/k6a4tWttQo

— Today FM News (@TodayFMNews) September 23, 2015