President Barack Obama is determined to find ways to draw "lasting value" from the visit of Pope Francis to Washington next week on shared goals such as tackling climate change and economic inequality, White House aides said Thursday. But they also acknowledged that the pope speaks his mind and could well say things that don’t jibe with Obama administration policies.

"The pope is a very independent figure," said Charlie Kupchan, senior director for European affairs at the National Security Council. "We don’t know what he’s going to say until he says it. We are fully expecting that there will be some messages with which we may respectfully disagree or have differences."

Either way, says deputy national security adviser Ben Rhodes, "the pope’s voice could not be more timely and important. He’s struck a chord."

Rhodes conceded that there’s always a political context to events in Washington, but said the pope "operates on a different plane" that causes people to think. Areas of difference between Obama and the pope include abortion and same-sex marriage.

Even when there are disagreements, Rhodes said, "we welcome the pope’s voice and leadership."

Unlike during a visit from a typical foreign leader, Kupchan said, the Oval Office conversation between the president and the pope will be "less about material deliverables and more about the themes."

Kupchan, who traveled to the Vatican in June to help lay the groundwork for the visit, said the president charged his team from the beginning with "ensuring that this visit has lasting value and is as meaningful as possible." The White House is looking for ways to turn the shared objectives of the pope and the president into concrete steps and new initiatives, he said, but he declined to identify specifics, saying only to stay tuned for details.

The White House is opening its back lawn to some 15,000 people for the pope’s arrival ceremony on Wednesday, and that throng will include Catholic leaders and parishioners from around the country, as well as representatives of other religions and people who simply are enthusiastic about the pope’s leadership. Obama and the pope will meet one-on-one in the Oval Office after the welcoming ceremony.

For all of the enthusiasm about the visit, White House press secretary Josh Earnest tacked on a practical warning. "Traffic’s going to be a mess," he predicted. Earnest took note that the government is encouraging federal workers in Washington to telecommute during the pope’s visit.

If 15,000 people do attend, that will surpass the more than 13,500 who were invited for Pope Benedict XVI’s arrival ceremony in 2008. Some 6,000 attended Pope John Paul II’s arrival in 1979.

While in Washington, the pope also will address Congress and celebrate Mass at the basilica.

Vice President Joe Biden, the first Catholic vice president, plans to participate in all the major Washington events and will lead the farewell ceremony for the pontiff in Philadelphia, the last stop on his U.S. visit, Biden’s office said. Biden called Francis "a moral rudder for the world on some of the most important issues of our time."

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