BERLIN (AP) — President Barack Obama joined the leaders of key European countries in Germany on Friday to discuss an array of security and economic challenges facing the trans-Atlantic partners as the U.S. prepares for President-elect Donald Trump to take office in January.

Obama's meeting with the leaders of Germany, Britain, France, Italy and Spain was likely his last in such a setting before he leaves office. The session expands on lengthy talks he held the day before with German Chancellor Angela Merkel.

Gathered around a circular table in Merkel's Chancellery, the leaders exchanged pleasantries but made no substantive remarks as reporters were allowed in briefly for the start of the meeting. A number of the leaders planned to deliver statements or take questions from reporters following the meeting.

Since Obama's arrival on Wednesday on his sixth and last trip to Germany as president, he and Merkel have focused several meetings on issues of globalization and trans-Atlantic cooperation. The talks come largely in the context of what the election of Donald Trump will mean to efforts to seek peace in Ukraine and Syria, the strength of the NATO alliance, trade agreements, efforts to fight climate change, and other pressing matters.

At a news conference with Obama on Thursday, Merkel diplomatically said she was approaching the incoming Trump administration "with an open mind."

Around the world, many are looking to Merkel — one of the longest serving leaders of a major world power, leader of Europe's largest economy and one of the biggest U.S. trade partners with the U.S. — for leadership as Obama leaves office.

Obama seemed to underscore that reality as he effusively thanked Merkel for her "deep friendship." He said he couldn't "ask for a steadier or more reliable partner on the world stage," while adding that if she chooses to run again for a fourth term next year, he'd vote for her — if he could.

Joining the two leaders Friday are the heads of countries at the center of many of the European Union's coming challenges.

British Prime Minister Theresa May is preparing her country for negotiations to leave the trade bloc. Spain's Prime Minister Mariano Rajoy faces economic woes in his country that have contributed to financial instability in the EU. Italian Prime Minister Matteo Renzi's already shaky economy has been rocked by tens of thousands of refugees. And French President Francois Hollande's socialist government faces a major challenge from the far-right in elections next year.

Trump has applauded the British decision to exit the EU, or "Brexit," and has had meetings with Nigel Farage, leader of the U.K. Independence Party and a key player in the British decision to leave. For his part, Obama said Thursday his hope was that the Brexit negotiations be "conducted in a smooth and orderly and transparent fashion and preserve as closely as possible the economic and political and security relationships between the UK and EU."

Still, he noted that he considered the EU "one of the world's great political and economic achievements."

Germany has emphasized that it respects the British decision to leave, but that the United Kingdom won't be able to cherry-pick what parts of the EU it wants to keep, and what not.

On other issues, Obama said he hoped for continuity of U.S.-European relations under Trump, saying "how important it is that we work together."

Obama said that "continued global leadership on climate in addition to increasing private investment and clean energy is going to be critical." He added that the U.S. would "continue to stand united with Germany and our NATO allies" in Afghanistan, and that on the refugee crisis he had put in place more robust support from Washington and that he was "hoping that continues beyond my administration."

Following his meetings in Berlin, Obama heads to Peru, the final leg of his last foreign tour, for an Asia economic summit.