Obama, pope unite for action on migrants, climate

President Barack Obama and Pope Francis married their political and spiritual power to urge action on immigration and the environment Wednesday, during the popular pontiff's maiden White House visit.

America's first black president offered the first Latin American pope a stately and effusive welcome on the South Lawn, praising his moral leadership on issues that politics has struggled to address.

Speaking in fluent but accented English, the 78-year-old Argentine pontiff returned the warm blessings of his host.

"As the son of an immigrant family, I am happy to be a guest in this country, which was largely built by such families."

Similarly, as many US conservatives question the very existence of man-made climate change, Francis and Obama made a de facto joint appeal for action on the issue.

"It seems clear to me also that climate change is a problem which can no longer be left to a future generation," Francis said.

The pontiff will make two key speeches during his US visit, the address to Congress and another to the United Nations on Friday. Appeals on behalf of immigrants and climate change will be running themes, according to Vatican sources.

He will wrap up his historic six-day US trip on Saturday and Sunday in Philadelphia at an international festival of Catholic families.