LONDON • British Prime Minister David Cameron is due to publish today his appeal to the European Union's other 27 member-states, outlining Britain's conditions to stay in the EU.
Mr Cameron's letter is likely to be conciliatory. But it will unleash one of the most difficult political battles in Europe, as well as a close-run British referendum scheduled for next year.
In 2013, when his ruling Conservatives faced what seemed like a mortal electoral threat from the nationalist UK Independence Party (UKIP) which pledged to pull Britain out of the EU immediately, Mr Cameron promised he would renegotiate EU membership and let the electorate decide whether Britain should remain part of Europe.
UKIP ultimately failed to shake up British politics, but Mr Cameron's promise has to be kept, if only to silence his anti-European backbench MPs. And officials in London agree it is in their interest to hold the referendum soon, while the government's popularity still holds up.
There is no doubt where Mr Cameron wants this process to end. "What I want for my country is to reform the European Union, to make it better, and then recommend that we stay in the European Union because we need those trade links, we need those markets open, " he told the recent Conservative Party conference. Still, the road ahead remains unpredictable.
Yet the toughest British demand remains unresolved: That of imposing a ban on EU citizens claiming welfare payments during the first four years of their residence in Britain.
Mr Cameron knows that he has to wring out serious concessions from Europe if he is to persuade a perennially eurosceptic public to vote "yes" to Britain's continued EU membership. But he is also aware that no other EU member-state is willing to renegotiate existing treaties. The letter he is circulating to his European counterparts today is attempting to straddle a delicate line between demanding concessions, which are not too consequential, but still sound serious enough to be trumpeted as a major diplomatic victory for Britain.
That's certainly the case with Mr Cameron's demand that Britain should be exempt from the application of a promise contained in the EU founding treaties, which pledge all member-states to work towards "an ever-closer union".
This is largely a general aspiration, but one often highlighted by opponents of the EU as proof that the organisation wants to destroy Europe's nation-states.
Mr Cameron will be able to obtain a statement from his counterparts that although that provision stays in place, it does not preclude individual countries from proceeding along the way of European integration at their own speed.
Largely declaratory is also another British demand, that the EU should pledge itself to open markets and free trade. The EU Commission has already issued, last month, its new trade strategy which emphasises Britain's liberal trading priorities, and repeating this agenda will not tax EU leaders unduly.
The British are also likely to get their way with a more difficult demand: That, as Mr Cameron puts it, London, which serves as Europe's biggest money centre, "will face neither discrimination nor additional costs" because Britain refuses to adopt the euro as its currency. That annoys a number of countries led by France, which claim the Brits want all the advantages of a free market with none of the regulation.
Nevertheless, in discussions in Berlin last week, German Finance Minister Wolfgang Schaeuble appears to have agreed that the British will be granted such a concession; what is most likely to happen is a promise that any future EU financial decisions will require a "double majority vote" of both countries in the euro zone, and those outside it.
Yet the toughest British demand remains unresolved: That of imposing a ban on EU citizens claiming welfare payments during the first four years of their residence in Britain. The British claim this is necessary to prevent the phenomenon of "welfare shopping", of people coming to Britain just to draw on its extensive welfare payments.
But many EU states view this as an attack on the fundamental principle of the free movement of people in the Union.
Critics of Britain's EU membership are already dismissing Mr Cameron's negotiating stance as "a cave-in". And opinion polls suggest a very tight result in the referendum which now looks likely next June.
The only advantage Mr Cameron has is that his opponents can offer no viable alternative to EU membership, apart from Britain's retreat into a "splendid isolation".