[WASHINGTON] President Barack Obama wants to help European leaders struggling to deflect a dagger aimed at the heart of the continent's political unity.
It's the combined impact of home-grown terrorism, mass migration from the Middle East and North Africa, sluggish economic growth and a groundswell of nationalist sentiment.
The US president arrived Thursday evening for a visit to Britain and Germany, where he will hold a summit with leaders of Europe's four largest economies. He came directly from a conference in the Middle East with Saudi King Salman and leaders of other Persian Gulf Arab states, a meeting at which the Syrian civil war and regional instability driving migration to Europe figured prominently.
Economic and cultural ties between the nations of Europe haven't been so strained since the Maastricht Treaty created the European Union in 1993. An influx of more than a million migrants last year has given new life to xenophobic political parties.
Terrorist attacks in Paris and Brussels have fueled concern about the continent's lenient border controls and internal security. And on June 23 voters in Britain will decide whether to leave the union, a move that Prime Minister David Cameron's government has said would grievously damage both the British and European economies.
"It's the confluence of these crises that is so striking," said Karen Donfried, a senior Obama adviser on Europe until 2014 who's now president of the German Marshall Fund of the United States. "Certainly the White House is taking note."
A fracturing of the 28-nation EU or a descent into dysfunction would undermine growth prospects for an economic bloc that is America's largest trading partner and would threaten cohesion among the US's bedrock allies.
In the worst case, divisions could unravel a project of integration that, since its inception as a six-nation coal and steel trade bloc in the aftermath of World War II, has maintained a rare period of extended peace among the major nations of a continent once racked by warfare.
Mr Obama arrived in London ready to enter the debate on the future of Europe, albeit aware of the delicacy of a foreign leader taking sides on matters that are essentially internal European issues.
London Mayor Boris Johnson, who favors leaving the EU, told the Associated Press "it's paradoxical that the United States, which wouldn't dream of allowing the slightest infringement of its own sovereignty, should be lecturing other countries about the need to enmesh themselves ever deeper in a federal super-state."
Still, support for European unity has been a foundation of US global strategy under both Democratic and Republican administrations for decades.
Mr Obama urged British voters "with the candour of a friend" to reject a so-called Brexit and wrote of the "deep interest" of the US in the outcome, in an op-ed published by the Daily Telegraph newspaper in London shortly after he landed.
"The European Union doesn't moderate British influence - it magnifies it," Mr Obama wrote.
"Now is a time for friends and allies to stick together."
He is likely to amplify the message at a news conference Friday in London and at a town hall for young people on Saturday, as well as in a speech in Germany on Monday.
As a presidential candidate, Mr Obama attracted his largest crowd of the campaign at an outdoor rally in Berlin in 2008, with estimates that as many as 200,000 people attended. He remains a popular figure in Europe.
76 per cent of Britons and 73 per cent of Germans said they had confidence in him to do the right thing in world affairs, according to Pew Research Center polls published last year. Only 58 per cent of Americans agreed.
Mr Obama is even more popular among Europe's youth, and the president's schedule in Britain, including the event for young people, is "very clearly geared at driving youth turnout in the referendum because young people are more pro-European," said Jacob Kirkegaard, a senior fellow at the Peterson Institute for International Economics in Washington.
While Mr Cameron's strategy to defeat Brexit emphasizes warnings of economic peril, that provides an opening for Mr Obama to lay out a positive vision for Britain's future in the European Union, Mr Kirkegaard said.
In Germany, Mr Obama's other stop, Chancellor Angela Merkel, the continent's dominant political figure, has been weakened by the flood of refugees into her country.
Mr Obama will offer his appreciation for Ms Merkel's "bold leadership in responding to the refugee crisis," said Charles Kupchan, the National Security Council's senior director for European affairs.
"The president wants to provide political support to her for doing so."
More than a million migrants entered Germany last year. The influx is credited for losses by Ms Merkel's party in three state elections last month as well as the rise of Alternative for Germany, a populist-right party whose platform calls for closing the nation's borders.
Even some Germans who support resettling refugees are dismayed by Ms Merkel's handling of the crisis, and particularly her concessions to Turkish President Recep Tayyip Erdogan in a bid to slow the flood of migrants.
In addition to a 6 billion euro (S$9.04 billion) aid package offered by the EU, Ms Merkel granted Turkey's request to prosecute Jan Boehmermann, a German satirist who lampooned Mr Erdogan in a bawdy poem. Members of Ms Merkel's governing caucus said the decision was anti-democratic.
Mr Obama will confer on Monday in Hanover with Ms Merkel, Mr Cameron, French President Francois Hollande and Italian Prime Minister Matteo Renzi regarding the Syrian civil war and strife in Iraq, Libya and Afghanistan that is fueling migration to Europe, as well as counterterrorism programs and a strategy to counter Russian President Vladimir Putin's aggressive moves in Eastern Europe.
Mr Obama's influence is inherently limited as a lame-duck president from a country that itself has only shown a minimal willingness to accept refugees.
"A president on his last lap who is worried Europe is going to fall apart isn't in a position to do a whole lot other than say, 'You know, I really think what you're doing is the right thing. I know I can't do a great deal, but I want to give you a shout-out,'" said Constanze Stelzenmueller, a fellow at the Brookings Institution, a Washington policy center.
Political discontent in Europe is exacerbated by its struggle to recover from the global recession. The continent has essentially suffered a lost decade, with uneven growth between the more prosperous north and languishing south.
High youth unemployment is dashing economic prospects for an entire generation along Europe's southern periphery, including Spain, Portugal, Italy, Greece and even France, where a quarter of people under 25 are unemployed.
Adjusted for inflation, the gross domestic product for the 19 countries sharing the euro has barely budged since the recession began at the end of 2007, up a total of less than four-tenths of a per cent through the end of 2015. By contrast, the US economy grew almost 10 per cent in the period.