Greenpeace has sent a clear message to President Donald Trump during his visit to the Vatican by projecting a message in lights on to the dome of St. Peter’s Basilica that read: Planet Earth First.

It seemed to be a play on Mr Trump’s “America First” slogan that has guided much of his young presidency. Climate change is one of the many issues on which Mr Trump and Pope Francis disagree.

Police allowed the lights to shine for “a few moments” before shutting down the peaceful protest.

The environmental campaign group's Executive Director Jennifer Morgan said: “We delivered to Trump a message that his first priority must be to people and planet, not the profits of polluters. Trump cannot stop the clean energy transition and should instead focus on accelerating it.”

The US is one of the largest emitters of carbon in the world, however Mr Trump hs repeatedly called climate change a “hoax” perpetrated by the Chinese in the past - a stance which appears to have softened a bit after his face-to-face meeting with Chinese President Xi Jinping.

China has become a leader in renewable energy investments, which topped new money pouring into the oil and gas industry for the first time in 2015 to the tune of $350 billion.

He also appointed former Exxon CEO Rex Tillerson as Secretary of State and a known climate denier, Scott Pruitt, to lead the Environmental Protection Agency (EPA).

However, Pope Francis took a far different stance in his 2015 encyclical, or papal letter, in which he called for the faithful to protect the planet.

He wrote that it was a “global problem which has grave implications: environmental, social, economic, political, and for the distribution of goods.”

The pontiff presented Mr Trump with a copy of the encyclical as a gift during his Vatican meeting.

The president has also caused consternation for many countries in the group of seven (G7) for not making a decision on whether to keep the US in the historic Paris Agreement on climate change.

Nearly 200 countries signed the deal in December 2015 and President Obama bypassed Congress in order to approve the deal, which took effect just days before the 2016 election.

Several alliances, including the 28-member military alliance North Atlantic Treaty Organisation (Nato) have declared climate change as a global security threat, especially in the Middle East where drought and famine are growing concerns.