(CN) - Hopes for a deal that will keep the United Kingdom in the European Union dimmed Wednesday ahead of a last-ditch round of talks between British Prime Minister David Cameron and the European Council, with leading EU lawmakers saying a U.K. exit would trigger the collapse of 28-member union.
Britain's potential secession from the EU is one front of what lawmakers called "a perfect storm" threatening the union. In fact, several of the storm's fronts are tied to the reasons some in the U.K. have advocated for the "Brexit," as European media outlets have called the secession movement.
Cameron has demanded a number of controversial reforms from EU lawmakers in exchange for persuading his countrymen to vote to stay in the union, in an election that could be held as early as June.
The reforms include an "emergency brake" that would allow Britain to limit social welfare payments to citizens of other EU member states residing in the U.K. Nations in Eastern Europe say the plan would discriminate against the large numbers of their citizens who work in Britain and runs contrary to the EU constitutional principle of freedom of movement.
Meanwhile, nations that use the euro have balked at Cameron's demand that Britain receive special safeguards against financial troubles in the 19-member eurozone - most recently seen during the Greek debt crisis and a large EU bailout of Portugal. France in particular has said it will veto any deal to keep Britain in the EU that includes this provision.
In a letter to his colleagues, European Council President Donald Tusk said of Thursday's summit, "There will not be a better time for a compromise."
He added, "After my consultations in the last hours I have to state frankly: there is still no guarantee that we will reach an agreement. We differ on some political issues and I am fully aware that it will be difficult to overcome them. Therefore, I urge you to remain constructive."
But European Commission President Jean-Claude Juncker said before meeting with Cameron Tuesday the Brexit is not an option.
"If I would say now that we have a plan B, this would indicate a kind of willingness of the commission to envisage seriously that Britain could leave the European Union," Juncker said. "We don't have a plan B, we have a plan A. Britain will stay in the European Union as a constructive and active member of the union."
And although the British royal family doesn't usually comment on political issues, Prince William on Tuesday made a speech that many in the British media viewed as thinly veiled backing of continued EU membership - although Kensington Palace said the speech wasn't about the EU per se.
"For centuries Britain has been an outward-looking nation. We have a long, proud tradition of seeking out allies and partners," the prince said. "Our ability to unite in common action with other nations is essential. It is the bedrock of our security and prosperity."
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