Pope Francis has called for further action on climate change saying that it was "a critical moment of history", on the first day of his visit to the US.

Speaking to a crowd of more than 11,000 people on the White House South Lawn, the pontiff said the problem could "no longer be left to a future generation".

President Barack Obama said the Pope reminded people "that we have a sacred obligation to protect our planet".

The Pope will later conduct the first canonisation on US soil.

The canonisation will be part of a Spanish-language Mass to be held at the largest Roman Catholic church in North America, and will elevate to sainthood the Spanish missionary who brought Christianity to what is now the US west coast.

The ceremony at the White House differs from most other state visits. Mr Obama and Pope Francis did not review the troops, as presidents typically do with other visiting leaders, because the pontiff does not control any armed forces.

The Pope will also not return to the White House in the evening as the guest at a lavish state dinner, seen as a highlight of most state visits.

At the afternoon Mass, Junipero Serra, a Spanish Franciscan who founded a mission in California in the 18th Century, will become the first Hispanic saint in the US.

But the decision to canonise the missionary has been criticized by Native Americans, who view him as someone who aggressively imposed Catholicism on their ancestors.

Pope Francis has in the past apologised for the treatment of indigenous people.