When Pope Francis meets Barack Obama at the White House on Wednesday, the president will bask in his guest’s moral authority and iconic popularity. But the first pontiff from Latin America is likely to exploit those assets to pressure his host on U.S. global economic leadership.

On Francis’s first full day in the country, Obama and as many as 15,000 guests will welcome him on the South Lawn of the White House. For the president, it’s an opportunity to showcase the pope’s support for his initiatives on income inequality, immigration and climate change.

“These are issues that are going to define our future, and the pope I think is providing an incredible sense of motivation that they can and must be addressed,” Deputy National Security Adviser Ben Rhodes said in a conference call with reporters. “The pope’s voice could not be more timely and important.”

Contentious issues involving Church doctrine on the family -- such as abortion rights and contraception coverage -- will be swept under the carpet of the Oval Office. But the pope, who called for “a poor Church for the poor” on his election, is expected to elevate his concern for the downtrodden and the excluded for a global audience.

“There are points of tension, and the role of the U.S. as a world leader in economic justice is certainly going to be an issue -- how much the U.S. is doing will be on the pope’s mind,” said veteran Vatican watcher John Thavis, author of The Vatican Prophecies. “The U.S. is in a position to drive some of these discussions, and the pope would like to see some leadership.”

At the White House on Wednesday morning, crowds began gathering well before sunrise to clear the security checkpoints before assembling on the South Lawn. A group of drummers banged on their instruments near the Treasury Department, and a man with a bullhorn disrupted the quiet near Lafayette Square on the north side of the White House complex.

Lines for those holding tickets to the White House ceremony grew after the gates opened at 5 a.m. Yellow and white Vatican flags were flying alongside U.S. flags around the White House ready for Francis’s arrival.

Extraordinary Pulpit

The political heft of the leader of the world’s 1.2 billion Roman Catholics will be underscored by crowds that security officials expect to be comparable to a presidential inauguration. Some 150,000 people may congregate on the route of his “popemobile” along the National Mall. Much of downtown Washington will be closed to traffic.

Francis faces a balancing act in crafting his message for the extraordinary pulpit that his first visit to the U.S. affords. He will be the first pope to address Congress, on Thursday, and then speaks to the United Nations General Assembly on Friday. He must tailor his criticisms of capitalism’s excesses for a country in which the philosophy is nearly a faith.