[MUNICH] European Union leaders head into a week of crucial diplomacy on Britain's future in the bloc with a US warning to avoid "Brexit" and concern that disunity could undermine regional security.
Days before EU national leaders try to thrash out a deal aimed at keeping Britain in, German Chancellor Angela Merkel's senior foreign-policy lawmaker, Norbert Roettgen, said Europe needs more unity, not less.
That followed a warning by US Secretary of State John Kerry that a British exit would weaken Europe just as it needs strength to deal with the twin challenges of terrorism and refugees.
"We cannot any longer delegate this matter of European security to the US," Mr Roettgen, who heads the German parliament's foreign affairs committee, said at the Munich Security Conference on Sunday. "We have to pour in a much, much higher amount of financial, political, military resources. We have as Europeans to care for our security - this is fundamentally new."
UK Prime Minister David Cameron needs approval from every other nation in the EU to secure a deal at a two-day summit starting Thursday in Brussels. That would pave the way for him to hold a referendum on staying in the bloc as early as June 23 and campaign against a British withdrawal.
As a week of diplomacy gets under way, the UK's role in fighting Islamic State militants and Europe's divisions over how to handle refugees underscore the stakes.
"Europe is going to emerge stronger than ever, provided it stays united and builds common responses to these challenges," Mr Kerry said to applause at the Munich conference on Saturday. "Obviously, the United States has a profound interest in your success, as we do in a very strong United Kingdom staying in a strong EU."
European leaders shouldn't underestimate the risks of an EU without Britain, according to Ian Bremmer, founder of New York-based consultancy Eurasia Group.
"Brexit would be significantly destabilising," he said in an e-mail. "It would take years to manage the unwind, further referenda would become likely and leadership on foreign-policy issues would become much weaker across the board."
While Britain would remain a member of the North Atlantic Treaty Organisation military alliance if it left the EU, the UK is raising that spectre of a Europe preoccupied with its own unraveling.
"Without Britain, Europe would lurch very much in the wrong direction," UK Foreign Secretary Philip Hammond, said in a Sunday interview with the BBC.
"The thing we have to remember is there's a real fear in Europe that if Britain leaves, the contagion will spread," Mr Hammond said. "People who say we'd do a great deal with Europe if we left forget that the countries remaining in the European Union would be looking over their shoulder at people in their own countries saying, 'If Britain can do it why can't we?'"
Mr Cameron isn't assured of victory. The latest ComRes poll found 21 per cent of British voters expect him to get a good deal from his renegotiation, while 58 per cent doubted the package would be a success. Almost half - 45 per cent - had no idea whether they'd be personally better or worse off if Britain left the EU or stayed in, according to the poll.
Not all EU governments have the UK's future in Europe uppermost on their minds. Rather than looking westward, Polish President Andrzej Duda said he's fretful about the menace to his east.
"Of course we have problems, also in the European Union - migration crisis, Brexit and others," Mr Duda said at the Munich conference on Saturday. "But our security, military security especially, is now the most important when we see the situation for example in the Ukraine."