Closing the final leg of his last European visit as US President on Friday, Barack Obama met with leaders from five European countries as they sought reassurances following Donald Trump's US election victory.

Faced with the uncertain future of a transatlantic relationship with Trump at the helm, Friday's meeting marked the first time since the Republican win that German Chancellor Angela Merkel, UK Prime Minister Theresa May, French President Francois Hollande, Spanish Prime Minister Mariano Rajoy and Italian Prime Minister Matteo Renzi all gathered together, along with Obama.

A statement issued by the White House shortly after the summit said Obama agreed with his European counterparts that they need to continue working together as part of multilateral bodies such as NATO.

"The leaders agreed on the necessity of working collectively to move the transatlantic agenda forward, particularly onbringing stabilization to the Middle East and North Africa, as well as securing diplomatic resolution to the conflicts in Syria and eastern Ukraine," the White House said.

The unanimity between the six leaders on Friday came in light of comments made by Trump, in which he called into question the almost 70-year-old security shield for US allies.

Ahead of last week's US presidential election, the president-elect also vowed to withdraw from the hard-fought deal on Iran's nuclear program as well as the Paris Climate Agreement. Having described global warming as a "hoax," Trump has raised concerns among environmentalists and climate scientists that the US will once again pull out of an international climate deal.

Global warming 'hoax'

In light of Trump's campaign promises to tear up US free trade deals, the future of TTIP negotiations also look uncertain. Following his election, the European Commission has already put TTIP talks on hold.

Ahead of Friday's summit, however, Obama voiced a hint of cautious optimism that Trump could change his position once he takes on the role as president.

"There's something about the solemn responsibilities of that office ... that forces you to focus, that demands seriousness," Obama said at a press conference following a meeting with Merkel.

Call for EU unity

As the UK prepares to leave the EU following June's shock Brexit vote, Obama also stressed the importance of a united Europe, and urged the 28-member bloc not to take the transatlantic relationship for granted.

"The EU remains one of the world's great political and economic achievements, and those achievements should not be taken for granted," he said.

"The achievements that we have seen on this continent in contrast to a divided Europe of the previous century, are ones that remind us of how important it is that we work together," Obama added.

Trump's friendly disposition towards Russian President Vladimir Putin also raised questions on his attitude toward the Kremlin's support of Syrian President Bashar al-Assad, as well as Moscow's role in the conflict in eastern Ukraine.

The six leaders at Friday's summit agreed that sanctions against Russia should remain in place until it meets its commitments to resolving the conflict. 

Ahead of Friday's talks, Obama said that he hoped Trump "is willing to stand up to Russia where they are deviating from our values and international norms."

The outgoing US president went on to caution Trump against the temptation to "cut some deals with Russia" that hurt smaller countries because it may seem "convenient at the time."

Goodbye Berlin

The meeting on Friday marked the end of Obama's two-day visit to Berlin where he held bilateral talks with longtime ally and friend Merkel, who is expected to announce soon - perhaps as early as Sunday - whether she will run for a fourth term in next year's federal election.

Acknowledging that she would have heavy international burdens to shoulder, Obama said: "I wish I could be there to lighten her load somewhat. But she's tough."

As a parting gift on Friday, Merkel presented Obama with a German "Weihnachtspyramide." The traditional Christmas decoration dates back to the Middle Ages. Traditionally, people were said, in dark times, to try and avert disaster with the power of the pyramid's light - an arguably fitting gift amid the apprehension surrounding Trump's pending presidency.

In a press conference with Spain's Rajoy on Friday, Merkel said: "One person cannot solve everything, but together we are strong."

"I want to accomplish what is my task as German chancellor. On the one hand I have my duty to the people in Germany. But that also implies working for the cohesion and success of Europe," Merkel added.

On arriving in Peru to complete the final leg of his last foreign tour as US president, Obama will turn his attention to his final Asia-Pacific Economic Cooperation leaders' meeting. Top of the agenda will be how to improve trade relations, now that the TTIP agreement will no longer be considered this year.

Merkel, meanwhile, was due on Friday afternoon to hold individual talks with each of her European counterparts who were present in Berlin.