Barack Obama: 'We can't hide behind a wall'

— -- Sitting in front of Berlin's Brandenburg Gate -- one of Germany's most famous landmarks -- former U.S. President Barack Obama made a thinly veiled jab at President Donald Trump at a conference celebrating the 500th anniversary of the Protestant Reformation.

“In this new world that we live in, we can’t isolate ourselves, we can’t hide behind a wall,” Obama said in regards to immigration and foreign aid.

Obama was joined onstage with the most powerful leader in Europe, German Chancellor Angela Merkel.

The two leaders -- who worked closely together during Obama’s presidency -- held a discussion on “Being Involved in Democracy: Taking on Responsibility Locally and Globally.” Civic engagement has emerged as an important theme in Obama’s early post-presidency, and the Obama Foundation chose to sponsor the event as a way to highlight the role of faith-based organizations in local communities.

Obama’s first foreign speaking engagement comes at a time when all eyes are on Trump’s first trip abroad. Merkel sat down with Obama just hours before she travels to Brussels to meet with Trump and NATO leaders.

And while Obama did not mention Trump by name, the conversation steered toward politics and his differing worldview. Both Obama and Merkel reflected on their policies on health care, foreign aid and refugees.

Obama said progress toward universal healthcare in the U.S. is “in peril” as Republicans try to repeal and replace Obamacare.

"We are unique among advance countries in that we don't have universal health care. My hope was that I was able to get 100 percent of people health care while I was president. We didn't quite achieve that but we were able to get 20 million people healthcare who didn't have it before," Obama said. "Certainly I have some regrets that we weren't able to get everybody health care and obviously some of the progress that we made is now in peril...but the point is that for those 20 million people their lives have been better."

Obama also discussed human rights, saying it's important to "push back against those trends that would violate human rights or that would suppress democracy or that would restrict individuals freedoms of conscious or religion."

He went on, "For example I look at a place like Syria that despite our best efforts you still have a war taking place, millions of people displaced, hundreds of thousands killed...it is going to require everything we can do to recognize that what happens on the other side of the world or in these other countries...that it has an impact on us and we're going to have to be invested in trying to help those countries achieve peace and prosperity. And as president I did not always have the tools that I wanted to affect those kinds of changes, but at least we tried.”

Reflecting on his life post-White House, Obama said he's mostly been trying to catch up on sleep.

"It's only been four months so I'm not sure I have the best historical perspective. Mostly I've been trying to catch up with my sleep. I've been trying to make sure that I'm spending more time with Michelle so that she forgives me for all the times that I've been away. I've been spending time with my daughters," he said.