Pope Francis has warned against rising popularism and the danger of crises allowing rulers such as Hitler to sweep to power.

But the head of the Catholic Church also urged followers not to judge Donald Trump too quickly.

The pontiff made the comments in a wide ranging interview published on Sunday by the Spanish newspaper Le Pais. He said he would wait to see the new US President's specific policies before coming to an opinion on him. 

But at the same time he warned Europeans against populism, saying they should not repeat the same mistakes as in the 1930s when they turned to "saviors" to resolve the economic and political crisis only to end up at war.

"Crises provoke fear, alarm. In my opinion, the most obvious example of European populism is Germany in 1933... A people that was immersed in a crisis, that looked for its identity until this charismatic leader came and promised to give their identity back, and he gave them a distorted identity, and we all know what happened," the Pope said.

"In times of crisis, we lack judgment, and that is a constant reference for me... That is why I always try to say: talk among yourselves, talk to one another," he added. 

On Friday, as Trump was taking office, Francis had urged him to be guided by ethical values, saying he must take care of the poor and the outcast during his time in office.

But on Sunday said: "I think that we must wait and see. I don't like to get ahead of myself nor judge people prematurely.

"We will see how he acts, what he does, and then I will have an opinion. But being afraid or rejoicing beforehand because of something that might happen is, in my view, quite unwise. It would be like prophets predicting calamities," he said.

During the presidential campaign Francis point blank denied Trump was a Christian if he pursued policies of deporting unregistered immigrants and building a wall on the border with Mexico. 

"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian. This is not the gospel," he said during the election campaign.

Francis extended warm greetings to Trump after he was sworn in as the 45th US President on Friday.

In a message sent from the Vatican the pontiff said: "At a time when our human family is beset by grave humanitarian crises demanding far-sighted and united political responses, I pray that your decisions will be guided by the rich spiritual and ethical values that have shaped the history of the American people and your nation's commitment to the advancement of human dignity and freedom worldwide."

He added: "Under your leadership, may America's stature continue to be measured above all by its concern for the poor, the outcast and those in need who, like Lazarus, stand before our door."