PARIS/LONDON (Reuters) - French President Francois Hollande reckons there is work still to be done to secure a deal at a European Union summit this week to help keep Britain in the EU, a presidency source said after a visit by British Prime Minister David Cameron.
On a final push to rally support in Europe before Thursday's summit in Brussels, which could sway Britons voting in a referendum to stay or leave the EU, Cameron met Hollande for an hour and will meet members of a wary European Parliament on Tuesday.
"There's a political will to conclude in Brussels," the French presidency source said. "There is still work to be done, especially on economic governance."
The French are seeking to limit any British right to interfere in euro zone decisions, and ensure Britain commits to allowing further integration of the euro area, a diplomatic source said.
Last week, France secured some amendments that Paris said were needed to ensure that efforts to balance the euro zone's "ins" and "outs" did not give the City of London an unfair edge.
Two weeks after a draft accord won initial backing from fellow national leaders who will try to iron out remaining differences with Cameron, Tuesday's meeting with EU lawmakers highlights some of the risks of political turbulence before a British referendum.
Not only was a plan to meet leaders of all the European Parliament's party blocs cancelled -- allowing Cameron to avoid a confrontation with his eurosceptic arch critic Nigel Farage -- but the need for the assembly's approval of key elements raised questions about how binding any summit agreement will be.
Speaking before the meeting with Hollande, Cameron's spokeswoman rebuffed questions in London about the extent to which the European Parliament could later block reforms agreed by the leaders after Britons vote in the referendum, possibly in June.
Insisting that senior parliamentarians have indicated their general support, and refusing to speculate on the "hypothetical" situation where the legislature refuses to pass laws that the leaders agree on, the spokeswoman said: "We have been very clear this is a legally binding, irreversible decision."
Leading members of parliament have been involved in negotiations and say they are willing to work on legislation to, for example, help Britain discriminate against EU workers on benefits to discourage immigration.
But the 750-seat chamber is dominated by supporters of closer European integration, jealous of their powers and little given to voting discipline within their trans-national parties -- creating a risk of delay or amendment to legislation that Farage, a seasoned anti-EU campaigner was quick to highlight.
In a statement describing Conservative leader Cameron as "gutless" for choosing to meet only leaders of the three main parties rather than all eight, including himself, Farage said:
"He knows that not only is his deal pitiful but that ... I would be able to expose the fact that even if he wins the referendum, the parliament will veto its terms."
If the 28 national leaders agree to a deal on the basis of a draft brokered by summit chairman Donald Tusk, Cameron is expected to call the referendum and campaign to stay in a "reformed European Union". The precise legal form of the accord is still under discussion but EU and British officials say it would have the force of a binding international treaty.
It would only come into force, however, after British voters backed continued EU membership. Only then would the European Parliament consider legislation, still to be drafted by the EU executive European Commission, to put some changes into law.
Cameron has said Tusk's current offer will give Britain the ability to reduce immigration from the rest of the EU, protect its sterling-based finance industry from being disadvantaged by the majority of EU states in the euro zone and ensure Britain's right not to be drawn deeper into a political union in Europe.
In Bucharest, Tusk urged compromise to keep the bloc together. "This is a critical moment," Tusk told reporters after a meeting with Romania's President Klaus Iohannis.
"It is high time we started listening to each other's arguments more than our own. The risk of a break-up is real because this process is indeed very fragile and must be handled with care. What is broken cannot be mended," he said.
A diplomatic source said the British do not want any retreat from Tusk's proposals as Cameron has to have a deal he can sell to both the public, and the already unimpressed eurosceptics in his own Conservative Party.
After himself meeting Hollande in Paris on Monday, Tusk said he hoped for a deal in Brussels at the end of the week.
Additional reporting by Paul Taylor in Paris and Jan Strupczewski, Alastair Macdonald, Gabriela Baczynska, and Tom Koerkemeier in Brussels; Writing by Alastair Macdonald; editing by John Stonestreet