The journey will be difficult. The road will be long. I face this challenge with profound humility, and knowledge of my own limitations. But I also face it with limitless faith in the capacity of the American people.

It may be something that future generations are more open to, but I am pretty confident that for the foreseeable future, using the argument of nondiscrimination, and "Let's get it right for the kids who are here right now," and giving them the best chance possible, is going to be a more persuasive argument.

We are willing to uphold principles that have resulted in unprecedented prosperity and security throughout Europe and around the world. With the threat of climate change only becoming more urgent, Angela [Merkel] and I focused on the need for American and E.U. leadership to advance global cooperation.

Since taking office, I've made it clear that the United States was prepared to begin a new chapter of engagement with the Islamic Republic of Iran. We offered the Iranian government a clear choice. It could fulfill its international obligations and realize greater security, deeper economic and political integration with the world, and a better future for all Iranians. Or it could continue to flout its responsibilities and face even more pressure and isolation.

We have to find ways in which, collectively, we agree there's some things that government needs to do to help protect us, that in this age of non-state actors who can amass great power, I want my government - and I think the German people should want their government - to be able to find out if a terrorist organization has access to a weapon of mass destruction that might go off in the middle of Berlin.

If we can't meet with our friends, I don't know how we're going to lead the world in terms of dealing with critical issues like terrorism.

Climate change constitutes a serious threat to global security, an immediate risk to our national security, and, make no mistake, it will impact how our military defends our country.