LONDON — Pope Francis and British Prime Minister Theresa May have criticized the Trump administration's policy of separating migrant children from their families at the U.S. border with Mexico, joining a growing number of world leaders to condemn the policy.

Speaking in an interview with Reuters, which was conducted at the Vatican on Sunday and published Wednesday, the pope said he supported recent statements by U.S. bishops who called the separation of children from their parents "contrary to our Catholic values" and "immoral."

"It's not easy," he said in a wide-ranging interview where he discussed global migration issues at length. "But populism is not the solution."

Meanwhile, U.K. Prime Minister May delivered her latest public rebuke to President Donald Trump, describing the family separation policy as "wrong" during her weekly parliamentary question and answer session in London on Wednesday.

Responding to a question on whether her government was still planning to "roll out the red carpet" for Trump's scheduled visit to the U.K. next month in spite of public uproar, May spoke out against the policy.

"The pictures of children being held in what appear to be cages are deeply disturbing. This is wrong, this is not something that we agree with, this is not the United Kingdom's approach," May told parliament.

May's comments follow criticism from a number of other world leaders.

Iran's supreme leader, a frequent critic of U.S. policy, denounced the separations in comments published on his official website on Wednesday.

"Seeing the images of the crime of separating thousands of children from their mothers in America makes a person exasperated," Ayatollah Ali Khamenei said, according to his website. "But the Americans separate the children from the immigrant parents with complete maliciousness."

Mexico's foreign minister, Luis Videgaray, said the administration's actions were "cruel and inhumane" on Tuesday.

"This is a clear violation of human rights and puts children, including those with disabilities, in a vulnerable situation," Videgaray told a news conference in Mexico City, where he urged the U.S. to reconsider the practice.

French government spokesman Benjamin Griveaux also condemned the separations on Tuesday. “We do not share the same model of civilization, clearly we don’t share certain values,” Griveaux said during an interview with France 2 television. "“These images are shocking,” he added later.

United Nations Secretary-General Antonio-Gutteres warned on Monday that refugee and migrant “children must not be traumatized by being separated from their parents,” after the U.N.'s refugee agency had earlier issued a statement warning the U.S. against "putting families through the lasting psychological trauma of child-parent separation.”

Non-governmental organization Refugee International issued a series of report cards on Wednesday to mark World Refugee Day. It gave the Trump administration an F for its treatment of refugees, citing its undermining of longstanding U.S. policy and refugee law domestically through the "inhumane separation of families," as well as its restricting of lifesaving humanitarian aid overseas.

Trump has strongly defended his administration's actions, which have seen at least 2,342 children separated from their parents since the policy was first implemented in May.

"Democrats are the problem," Trump said on Twitter on Tuesday. "They don’t care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our Country."

He struck a different tone with House Republicans on Tuesday night, however.

"We gotta take care of separation," Trump said, according to people who were in the closed-door meeting in the basement of the Capitol. "It's too nasty."

The State Department, meanwhile, released a statement to commemorate World Refugee Day. "We will continue to help the world's most vulnerable refugees, reflecting the deeply held values of the American people," Secretary of State Mike Pompeo said.