David Cameron will spell out his case for reforming the European Union as he prepares for next week's crunch summit in Brussels.
The Prime Minister is expected to use an address to the annual St Matthew's Day banquet in Hamburg, Germany, to set out the "wider agenda" behind his renegotiation of Britain's EU membership.
It will be his final set-piece speech on the issue before meeting the other EU leaders in the Belgian capital on February 18 and 19, knowing that he needs all 27 to back the deal hammered out with European Council president Donald Tusk.
"It will be about setting out the case, talking through the proposals, talking about where we are, reminding people of some of the reasons why we are taking this course of action," a No 10 spokesman said.
The Prime Minister received a sharp reminder of the opposition at home, with more than 130 Conservative councillors writing to warn that he risks splitting the party unless he accepts his renegotiation has failed and he campaigns for Britain to leave the EU, the Daily Telegraph said.
"You made clear that if you did not get the deal you wanted in Europe you would not rule out campaigning for Britain to leave the European Union yourself, and we hope you will now unite your party and Britain in doing so," they wrote.
Mr Cameron's visit to Germany will be a chance for him to have further consultations with Europe's key power broker, German chancellor Angela Merkel, who will be in Hamburg.
But while she has been broadly supportive of the deal, Mr Tusk has warned that the political process remains "very fragile", with some leaders still harbouring reservations about the plan.
The PM has cleared his diary to hold talks with some of the doubters - including French president Francois Hollande, Greek prime minister Alexis Tsipras, Romanian president Klaus Iohannis and Czech premier Bohuslav Sobotka - ahead of the summit.
Negotiations on the final wording of the deal - which includes an "emergency brake" on benefit payments to EU migrants and a UK opt-out from "ever closer union" - look set to carry on down to the wire.
Foreign Secretary Philip Hammond said on Thursday that there was still only a "working draft" and there were outstanding issues to be addressed.
There has been speculation Mr Tusk could call a further emergency summit if next week's gathering fails to reach an agreement.
Mr Cameron is anxious to get a final deal in place in time for him to put the outcome to an in/out referendum on Britain's continued membership in June.
No 10 fears that any delay beyond the early summer could play into the hands of the "out" camp, making it harder for the Prime Minister to secure an "in" vote.
Out campaigners claimed that the latest revised text to emerge on Thursday represented a further watering down of a plan they had already dismissed as hopelessly inadequate.
Downing Street sources insisted that the substance of the deal remained unchanged with only "minor technical changes" to the draft wording.
Labour former shadow chancellor Ed Balls threw his weight behind Mr Cameron's EU welfare reform agenda, but warned there remained "a lot more to do" to persuade the country to vote to stay in.
"We have got to show our population that Britain's influence can be used to make real changes in Europe, and that's what David Cameron is trying to do through his renegotiation," the ex-MP told BBC Radio 4's Today.
"The point is though that we can only make those changes from the inside; we can't solve the problems of companies not paying their tax or Europe's failure to tackle the refugee crisis from the outside.
"We need to win this referendum but there is still a lot more to do to win that case."
He went on: "I think David Cameron was right to make the argument that we needed to move away from free movement. I support the argument he has been making.
"At the moment he looks like he is going to secure restrictions on benefits paid to migrants.
"I think in the end we will end up with moving away from free movement and (towards) national controls on the amount of economic migration.
"That I don't think will happen quick enough for the referendum but what we have got to do is say to people: let's stay in and win that argument over time."
Mr Cameron spoke by phone with Spanish PM Mariano Rajoy to discuss the renegotiation.
A Downing Street spokesman said: "They agreed that good progress had been made and that we should continue to work closely together for an agreement at next week's European Council."