Of course I have got concerns. Donald Trump and I differ on a whole bunch of issues.

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.

This is not some distant problem of the future. This is a problem that is affecting Americans right now. Whether it means increased flooding, greater vulnerability to drought, more severe wildfires - all these things are having an impact on Americans as we speak.

When Michelle and I decided that I would run for President, it was because of a shared belief in the power of community and connection, a commitment to the idea that we are our brothers' keepers.

We all know a lot of people who died in 9/11, the World Trade Center. A lot of money funding that mission is directly tied - from the 9/11 Commission, directly tied to Iran, Hezbollah, Hamas.

I think a basic principle of our Constitution is nobody above the law

The Russians can't change us or significantly weaken us. They are a smaller country. They are a weaker country. Their economy doesn't produce anything that anybody wants to buy, except oil and gas and arms. They don't innovate. But they can impact us if we lose track of who we are.