ABOARD THE PAPAL PLANE - Pope Francis suggested on Wednesday that hostility to immigrants was driven by irrational fear, as he headed to Central America, a staging area from where migrants try to enter the United States.

U.S. President Donald Trump has asked Congress to provide him with $5.7 billion to help fund a U.S.-Mexico border wall to keep migrants out - a demand the Democrats refuse to meet, leading to a partial shutdown of the federal government.

One of the reporters flying with the Pope to Panama told him he had recently seen a barrier designed to deter migrants that juts out into the Pacific Ocean in San Diego, the western edge of the U.S. border with Mexico, and described it as a "folly".

"Fear makes us crazy," Francis replied.

Immigration is expected to be one of the main themes of the pope's six-day trip to Panama. Underscoring his firm focus on the issue, Francis met eight refugees living in Rome before heading to the airport for his flight.

The Jan. 23-28 visit to Panama for the Church's World Youth Day is the pope's first foreign trip of 2019.

The 82-year-old pontiff is also scheduled to visit the United Arab Emirates, Morocco, Bulgaria, Macedonia and Romania this year, and said a visit to Japan was on the cards.

"I am going to Japan in November. Get ready," he told reporters on board his plane.

Francis said he also wanted to visit Iraq but had been advised it was still too dangerous.

A Vatican official said last year that Pope Francis would consider the possibility of an unprecedented visit to North Korea. He said such a trip would need "serious preparation" and there has been no sign that it might happen any time soon.