Donald Trump has shunned a direct plea from Pope Francis and withdrawn the US from an ambitious attempt to form a humane global approach to migration.

The US ambassador to the United Nations, Nikki Haley, told the UN's general secretary Antonio Guterres that Trump's administration was backing out of the UN global compact on migration, saying it impedes US sovereignty.

In a statement on Saturday, Haley said: 'America is proud of our immigrant heritage and our longstanding moral leadership in providing support to migrant and refugee populations across the globe ... But our decisions on immigration policies must always be made by Americans and Americans alone.'

She added: 'We will decide how best to control our borders and who will be allowed to enter our country. The global approach in the New York declaration is simply not compatible with US sovereignty.'

In doing so the US became the only country to refuse to take part in the discussions after all 193 UN member states unanimously agreed to a non-binding political declaration in 2016, the New York declaration for refugees and migrants, that pledged to uphold the rights of refugees, help them resettle and ensure they had access to education and jobs.

The announcement came just hour's before a major UN conference on migration began on Monday in Puerto Vallarta, Mexico, and will further cool already frosty relations between Trump's White House and the UN.

It will also heighten tensions between Trump and the Vatican after Pope Francis made a specific plea for world leaders to work together. Earlier this year the Vatican published guidance for governments with specific proposals for the Compact, including creating safe ways for people to flee conflict areas and enabling refugees to find work and education in their place of arrival.

Chris Bain, Director of Catholic charity CAFOD, said Trump was 'abdicating responsibility' towards the most vulnerable.

'This move should serve as a catalyst for others to step into a leadership role, just as politicians worldwide sought to do by redoubling efforts on climate change following Trump's withdrawal from the Paris Agreement,' he said.

'Governments would do well to look to the real leadership example set by the Holy Father, who has made clear that the unprecedented movement of people we are seeing across the world is a global phenomenon. As such, it requires a global response; not a renunciation of responsibility.'