Prime Minister David Cameron is to meet French President Francois Hollande in Paris shortly - the latest leg in his drive to negotiate new EU membership terms for the UK.
After the draft deal was published two weeks ago, an irate editorial in the French newspaper Le Monde fumed that the concessions made to Britain were "exorbitant".
And while some in Mr Cameron's own Conservative Party dismiss his renegotiation as a watery fudge, politicians in Paris have a very different view.
Of particular concern here is the question of future financial regulation. UK ministers, too, think this is the most important part of the whole renegotiation.
The issue is this: The majority of EU countries that have the euro are integrating further and building a banking union with common rules and regulations. That process will deepen in the coming years.
Mr Cameron wants legal guarantees that the eurozone will not rig the rules in a way that could harm the interests of countries that do not have the euro. But France frets that the UK is seeking special treatment for the City of London, that could harm the single market in financial services.
France is also concerned a new mechanism that would allow non-euro countries to escalate their concerns could clog up decision-making.
The UK insists it is not asking for any veto or competitive advantage, but this is likely to be the focus of the hastily arranged talks here this evening.
President Hollande also faces an election next year - and while he wants the UK to stay in the EU, he will not do a deal that gives his opponents a chance to claim he sold out to Britain.
Further reading on the UK's EU referendum
EU renegotiation: Did Cameron get what he wanted?
Referendum timeline: What will happen when?
The view from Europe: What's in it for the others?