BRUSSELS -- EU leaders are expected to strike a deal in the next two days to clear the way for British Prime Minister David Cameron to call a U.K. referendum as early as June on continuing membership in the European Union, according to diplomats closely following the negotiations.
The February 18-19 summit in Brussels is the culmination of weeks of negotiations on reforms contained in a proposal submitted this month by European Council President Donald Tusk to avoid the potentially catastrophic departure of a key EU member in what's been dubbed a "Brexit."
Cameron has countered Euroskeptics at home by pushing to keep Britain in the bloc if it can guarantee reforms that include increased power for individual members.
EU officials told RFE/RL that significant progress had been made in the last few days and weeks toward a compromise acceptable to all 28 EU member states.
But they acknowledged that the details would still need to be agreed among attendees in a session that could extend into the early hours of February 19.
The agenda for the bloc's heads of state and other officials also includes discussion of the ongoing migrant crisis, although no specific decisions are likely to emerge on how to cope with Europe's largest wave of refugees since World War II.
British critics have objected to a range of EU policies and quotas, but officials have particularly emphasized areas like bureaucracy, competitiveness, economic governance, and social payments and remittances.
U.K. challenges to the European Union's commitment to the free movement of people are likely to prove especially contentious, with policies coming under enormous strain as Syrian refugees and other migrants pour into Europe on an unprecedented scale.
The specter of possible exceptions for individual members has sometimes dogged the reform talks.
But German Chancellor Angela Merkel lent force to British concerns on February 17 by telling lawmakers that "these are not just about Britain's individual interests on some issues or questions; rather, it's about several points that are justified and understandable," according to AFP.
The most serious dispute, on benefits payments to foreign workers, pits London against a number of relatively recent EU entrants from postcommunist Central and Eastern Europe.
Cameron has been keen to stem the flow to Britain of labor migrants and Tusk has suggested an emergency brake on benefits for EU workers in the United Kingdom. Some eastern members agree in principle to such a mechanism but disagree on details, including its duration.
Tusk's original proposal also envisaged the benefits exception as available to all EU member states seeing a large influx of labor migrants from other EU countries, but a compromise could see that field narrowed to three countries -- Ireland, Sweden, and the United Kingdom -- who opened their labor markets to citizens of new eastern members when the latter joined 12 years ago.
Another dispute concerns the possible indexing of child benefits for U.K. workers from elsewhere in the bloc.
France has also signaled its unhappy with another British request that could allow countries that don't use the euro -- such as Britain -- greater access to decision-making in the powerful Eurogroup, comprising eurozone finance ministers.
'Taking Stock' Of Migrants
On the current migrant crisis that threatens to rebuild borders swept away under the Schengen agreement, diplomatic sources told RFE/RL that EU leaders at the summit will merely "take stock of the [migrant] situation without taking any decisions."
The prime ministers of the Czech Republic, Hungary, Poland, and Slovakia met in Prague on February 15 to discuss "an alternative plan" to stem the flow of migrants to Europe by bolstering Macedonia's and Bulgaria's borders with Greece -- a move that some observers see as just the latest threat to EU unity on a fraught issue.
Earlier this month, the EU gave member Greece three months to fix its border problems or risk suspension from the "borderless" Schengen zone.
Greece's neighbor, Turkey, is hosting millions of migrants who have fled fighting in Syria during the five-year war devastating that country.
If there is a deal in Brussels, Cameron is likely to call a referendum in the United Kingdom -- which hasn't had a direct vote on a major EU issue in more than 40 years -- that could be difficult to predict.
The European Union and the euro were buffeted by a sovereign-debt crisis in Greece that finally abated after public-spending and other reform commitments salvaged a massive bailout deal in 2015, but only after considerable brinksmanship and talk of a possible "Grexit."