Israel was founded in 1948 as a Jewish homeland, its neighbours are all Arab countries. And Israel has fought several wars against them since it was created. The U.S. has been a close ally of Israel, both countries have concerns about Iran's controversial nuclear program. But president Obama and Israeli prime minister Benjamin Netanyahu haven't always agreed on how to deal with Iran. During this visit, they're expected to talk about those differences.

Pope Francis has been formally installed as the new head of the Roman Catholic Church. The College of Cardinals elected the new Pope last wek, but he was officially inaugurated as Pope yesterday. During this ceremony in Vatican City, he gave a sermon and talked about how the Catholic Church shuold focus on carrying for the poor and the sick. Pope Francis also discussed the importance of respecting the environment.

There is a vehicle built especially for the church leader, it's called the Pope Mobile. President Obama gets his own car, too, and there is a difference between these two in cost. Pope Mobile, $565,000, the Beast, president Obama's car, 1.5 billion. But both vehicles are big on security, the Pope Mobile has bulletproof Plexiglas dome, the Beast is made from armour that's eight inches thick. And the tyres are reinforced with Kevlar on that. Yesterday, Pope Francis greeted some of the people who came to his inauguration, but he wasn't riding in the Pope Mobile. He was in this open air vehicle, security obvious a big concern for any world leader. Ben Wideman looks at some of the challenges involved in protecting the Pope.

It was a thrill for the crowds, Pope Francis walking out ont he street to press the flesh. But it wan't a thrill for his security. One Italian newspaper quoted a member of the Pope security detail and saying if he carries on like this, it will drive us all crazy. But the Vatican spokesman isn't panicking.

"The very confident security forces with the Pope, and they're with him, they've been watching him, they'll adept to his own movements and they will do their best to adept to new situations."

The bishop of Rome has been a targeted in the past. In 1981, Pope John Paul the second were shot four times by would be Turkish assassin in St.Peter's Square. In 2008, a German woman tried to drag Pope Benedict XVI to the floor. A year later, she tried to do the same thing. Papal security has been provided by the Swiss guard for centuries. Now they are bolstered by the Italian Secret Service and the regular police who keep an eye on the tens of thousands of visitors who come here everyday.

"Vatican City is one of the world's most popular tourist destinations, but at the end of the day, security can only do so much, after which, they have to put their faith in God."

And that seems to be the attitude of most Popes, says former Swiss guard Andreas Widmer.

"The first priority of the papacy isn't the security, the first priority is his ministry, and he knows what he needs to do for his ministry and we're gonna cope with that."

No easy task when dealing with a Pope who thus far has been most unpredictable. Ben Wedeman, CNN, Rome.