Donald Trump has said his proposed border wall cannot be 'immoral' because the Vatican City has its own 40ft defenses.

Speaking at the White House after meeting congressional Democrats yesterday he said the Vatican 'has the biggest wall of them all'.

Drones flying above the border could only take 'nice pictures' and only a wall would stop people crossing illegally from Mexico, he said.

The President has demanded $5billion to fund the wall he promised voters in 2016 but Democrats have refused to pay it, forcing a partial shutdown.

Donald Trump, pictured at the White House yesterday, said his proposed border wall could not be 'immoral' because of the fortifications around the Vatican

Tourists queue by the Vatican's huge outer walls, which Trump compared to the border wall he wants to build along the border with Mexico

'When they say the wall's immoral - well then you'd better do something about the Vatican, because the Vatican has the biggest wall of them all,' Trump said at the White House on Wednesday.

'The wall is immoral? Look at all of the countries that have walls, and they work 100 per cent.

'It's never going to change. A wall is a wall. We can have all the drones flying over the people last night as they tried to rush the border.

'The only thing that stopped them was the wall. If we have drones up there it's wonderful, we'll get nice pictures'.

The Vatican - the world's smallest sovereign state - is surrounded by high walls although visitors are free to enter and wander around St Peter's Square.

The 40-foot stone walls were originally built in 852 on the orders of Pope Leo IV following a devastating raid by Arab attackers.

In the 1640s, Pope Paul III expanded the fortifications, and added additional defenses.

The wall is seen in front of the dome of St Peter's Basilica in Vatican City. The fortifications were first built in 852 to keep out Arab raiders and were expanded in later centuries

President Trump stands by a border wall prototype in San Diego in March this year. He has demanded $5billion in funding for it

The Pope's Swiss Guard, established in 1506 by Pope Julius II and uniformed in blue, red, orange, and yellow, is still responsible for protecting him.

Nancy Pelosi has said the Democrats will pay 'nothing for the wall' as the stand-off in Washington continues.

A similar row erupted during the 2016 election campaign when Pope Francis said it was 'not Christian' to build walls rather than 'building bridges'.

Trump aide Dan Scavino hit back on Twitter with a map of the Vatican and its fortifications, saying: 'Amazing comments from the Pope- considering Vatican City is 100% surrounded by massive walls.'

The President has also pointed to security defenses at Barack Obama's home in Washington as justification for his border wall.

He tweeted: 'President and Mrs. Obama built/has a ten foot Wall around their D.C. mansion/compound. I agree, totally necessary for their safety and security. The U.S. needs the same thing, slightly larger version!'