George Osborne is to give more details of the UK's EU renegotiation demands in Berlin on Monday.
David Cameron has promised to speed up efforts to get a new deal for the UK ahead of an in/out referendum planned by the end of 2017.
He will shortly set out the UK's wish list in writing after pressure from EU leaders who say he has not been clear about what he wants from them.
Mr Osborne looks set to prepare the ground in a speech in Germany.
Speaking in York, at the launch of a new infrastructure commission, the chancellor said: "We are now starting to negotiate directly with our colleagues in Europe through the European Council, and setting out more detail of what we think is required."
He said he would use a trip to Germany next week to set out more details of the changes the government wants to see in the way the EU operates.
Asked about the possible timing of the UK's referendum, Mr Osborne said: "We will hold the referendum when we have a deal we can recommend to the British people."
Mr Cameron is to set out full details of the UK's demands in a letter to European Council President Donald Tusk.