Former President Barack Obama plans to visit Germany in May to sit down with German Chancellor Angela Merkel for a panel discussion on democracy, returning to the international stage after what will be four months out of the White House.

The panel, titled "Being Involved in Democracy: Taking on Responsibility Locally and Globally," will coincide with President Donald Trump's summer tour of Europe and is part of the 500-year anniversary of the Protestant Reformation.

Obama's visit on May 25 will occur the same day Trump is scheduled to appear at a NATO leaders' summit in Brussels, Politico reported Tuesday. It is unclear if Merkel, who the media has called the new leader of the free world since Trump assumed office, will attend the summit.

Bishop Heinrich Bedford-Strohm, chair of the Evangelical Church in Germany, said in a press release that he invited Obama in May 2016 to visit Germany for the Reformation anniversary.

The event, jointly sponsored by the German Protestant Kirchentag and the Obama Foundation, will bring together Obama and Merkel, who enjoyed a close relationship during the former's time in office, despite some tensions. The U.S. and Germany had to manage tense relations after Edward Snowden revealed in 2013 that the National Security Agency was intercepting Merkel's cell phone communications.

The relationship between Trump and Merkel has been less friendly, with the two at odds over several issues. The German chancellor, who had an open-door refugee policy until recently that Trump castigated, has been a critic of the president's travel ban. Trump has previously called the NATO alliance, of which Germany is a member, "obsolete." Germany and the U.S. have also expressed differences over international free trade agreements since Trump became president.

Still, the two said their meeting last month was productive, and they reaffirmed the importance of the U.S.-Germany relationship.

Obama has not kept quiet about his successor as some past presidents have done. A little more than one week after Trump took office, Obama said he was "heartened" by the anti-Trump protests occurring across the country and criticized his successor's executive order to curb immigration.