David Cameron is holding talks with the German Chancellor Angela Merkel in Berlin today - someone he needs to win over if he is to have any chance of pushing his EU reform plans through.
He is also due to meet the Polish Prime Minister today, as he wraps up his bid to renegotiate the terms of the UK's membership of the European Union with key leaders.
German Chancellor Angela Merkel refused to rule out treaty change as she met with David Cameron in Berlin to discuss his plans to renegotiate the terms of the UK's membership of the European Union.
Mrs Merkel said: "Of course we have the desire to work very closely together. We would like to be a part of the process that is going on in Great Britain at the moment and we would like to be a constructive partner in this process.
"I have also said wherever there is a desire there's also a way and this should be our guiding principle here as well."
David Cameron has begun a whirlwind tour of Europe to discuss his terms for renegotiating the UK's membership of the EU with key leaders.
Prime Minister plans a whistle-stop charm offensive with EU leaders this week.
Details of the In/Out referendum will be presented to Parliament in a Bill this morning.