Jean-Claude Juncker, the European Commission president, has said he is confident Britain will not vote to leave the EU.
David Cameron’s motive in holding a referendum was to make Britain’s membership permanent, Mr Juncker said in an interview with a German newspaper.
“Brexit is not a question which arises, it’s not desired by the British,” Mr Juncker told Süddeutsche Zeitung newspaper.
“Cameron wants to dock his country permanently to Europe.”
Although the question of Britain’s EU membership is not officially on the agenda at the talks, it is likely to come up.
Mr Cameron’s bid to reform the EU gained a major boost last week when Mrs Merkel said treaty change was not impossible after meeting with him in Berlin.
Mr Juncker refused to comment on what reforms Mr Cameron might be seeking.
“The British have to say what they want themselves,” he said. “We will look at this with all serenity.”
He said it was up to the other member states to respond to Mr Cameron’s demands, rather than the European Commission.
“On this issue, the Commission is neither striker for defender,” he said in a footballing analogy. “It is for the European Council and the member states to deal with the British wish list.”
Mr Cameron was said to be “heartened” after his talks with Mrs Merkel last week but got a less positive response from Mr Hollande and the Polish Prime Minister, Ewa Kopacz.
A close ally of Mrs Merkel on Monday cast doubt on whether treaty change would be possible before Britain’s referendum.
“I can’t see treaty change as a realistic option within the course of two years,” Norbert Röttgen, the chairman of the foreign affairs committee in the Bundestag.
Speaking in London, Mr Röttgen said Germany wanted to keep Britain in the EU but had to consider what was feasible.
Monday’s talks in Berlin will underline that Germany and France are forging ahead with closer integration.
Even as Mr Cameron canvases leaders for support, Mrs Merkel and Mr Hollande are holding their own talks with the European Commission chief.
Officially the talks are supposed to focus on the EU’s digital strategy, but Mr Juncker admitted they could cover other subjects.
“Greece is not the core of the talks, but it would surprise me if it didn’t come up,” he said
Alexis Tsipras, the Greek Prime Minister, took a new hard line writing in Le Monde over the weekend, accusing Europe’s creditor powers of issuing “absurd demands”.
“I do not share this idea that we’d have fewer worries and constraints if Greece leaves the euro,” Mr Juncker said.
“I say to Mr Tsipras repeatedly, we’ve had an election in Greece, but there are 19 democracies in the eurozone. An election result must be taken note of, but you have to respect the sensitivities of other countries.”
But Mr Juncker did concede that bail-out conditions had caused hardship in Greece.
“We were too careless with regard to the social consequences of crisis policy in individual countries,” he said. “Anyone who doesn’t see there is a humanitarian crisis in Greece is deaf and blind to what is happening there. But that doesn’t mean we need a totally different policy.”
Mr Juncker took a harder line with Hungary, warning that it could be thrown out of the EU if it went ahead with proposals to reintroduce the death penalty.
“If Hungary wanted to introduce the death penalty, that would be a ground for divorce,” he said. “A reason for divorce! One of my political beliefs is that there shall be no death penalty. Anyone who introduces the death penalty has no place in the European Union.”
Mr Juncker stirred controversy recently when he greeted Viktor Orbán, Hungary’s Prime Minister, with the words “Hello dictator”.
Mr Orbán’s relations with other EU leaders have been strained for some time over his close ties with Russia and authoritian policies.
His government has stressed it has no plans to reintroduce the death penalty, and says it only broached the subject because of increased public debate surrounding it.
Mr Orban said late last week he is ready to talk with Brussels but “is against anyone driving the country out of the EU and Nato”.
“For us Hungarians they are our family,” he said.