ROME (AP) — The U.S. ambassador to the Vatican said Tuesday he expects Pope Francis will call on the U.S. to rediscover the fundamental values "that made our nation great" — especially its long history of welcoming foreigners — when he visits next month and becomes the first pope to address Congress.

In an interview with The Associated Press, Ambassador Kenneth Hackett said he expected migration, income inequality, family problems and the environment to be raised by Francis during his Sept. 22-27 visit to Washington, New York and Philadelphia.

History's first Latin American pope will be making his first-ever trip to the U.S., where gay marriage is now the law of the land and where conservatives have cringed at his criticisms of the excesses of unbridled capitalism and largely ignored his calls for an urgent transition away from a fossil fuel-based economy.

"I'm not worried about the tense moments, really," Hackett said. "In my two years here I've come to realize that Pope Francis will say and do what he wants. And that, people find refreshing even if they disagree with him."

The disagreements — including in Congress and among Republican presidential candidates — have become more pointed since Francis released his economic-environmental manifesto "Praise Be," in which he denounced the "structurally perverse" global financial system that he said has exploited the poor and destroyed God's creation.

"I think he is mature in his ability to accept disagreement," Hackett said. "In fact, it almost seems at times that he encourages it."

Francis has spoken out strongly about the need for wealthy countries to "open doors" to migrants seeking a better life, and Hackett said that message is likely to have an impact in a country where Republican presidential contender Donald Trump has called for a massive border fence along the Mexican frontier and the deportation of some 11 million immigrants living there illegally.

Hackett said he expected Francis would "bring people to think about the values that made our nation great," and how Americans as individuals and a nation can recapture those values and make them more prominent.

"I think he'll call us to continue to engage with it (the world), don't throw any walls up around our nation, don't revert to isolationism," he said. "We are a nation of welcoming people, so that's where I think he will put his attention."

Aside from the Congress speech, Francis will address the United Nations. Hackett said he expected the pope would take advantage of the global U.N. stage to not just press his environmental agenda, but also raise the plight of the persecution of Christians in the Middle East and Africa.

In Philadelphia, Francis will preside over the World Meeting of Families, a big church rally aimed at inspiring Catholic families, including those in "non-traditional" unions. Hackett said Francis might allude to gay marriage, but that there are other issues affecting families today: poverty, divorce, violence in the family and single parents raising children.

"I have to believe that he will reiterate that value of mercy that he has brought up in so many other endeavors," Hackett said.

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