The prime minister told European leaders in Brussels Thursday that he will send EU President Donald Tusk details of the changes he wants and the issues to be addressed, a British official said. The letter, which may not be made public, will probably be sent in early November and form the basis of a “fuller discussion” the following month.

The pledge came amid signs of frustration at Cameron’s reluctance to spell out exactly what concessions he hopes to achieve before putting Britain’s membership of the 28-nation EU to a referendum by the end of 2017. Once Cameron sends the letter, the “real negotiations can start,” Tusk said in a Twitter posting welcoming the commitment.

“This process is well under way and making good progress,” Cameron told reporters in Brussels at the start of summit. “I’m confident we can get a good deal for Britain, we can fix those things that need to be fixed.”

Having met all his fellow EU leaders over the summer, Cameron is trying to build momentum ahead of the year-end summit. The risk is that if he is too public about his wish list, then every goal he fails to achieve will be used against him by those who want Britain to leave the EU in the popular vote that follows the renegotiation.

David Fuller's view

The EU’s journey to an unachievable and undesirable Federal State is stuck on a divisive and corrosive reef of socialism and dwindling democracy.  The defensive EU leaders – Merkel, Holland and Junker – are in no mood to give the UK the independence it requires and now demands.  Eastern European countries, at least those fortunate enough to escape the Soviet Union and Putin’s Russia, are not about to surrender their independence to the EU triad above. 

Cameron should cut his losses in terms of credibility on this issue by putting forward a clear list of demands agreed by his cabinet, which is also simultaneously published.  The EU triad would almost certainly reject the UK government’s sensible demands because they know that other countries would ask for more or less the same.  Cameron can then declare his love for a free, entrepreneurial Europe and join the ‘NO’ side of the UK’s forthcoming referendum which should be brought forward to avoid further distraction. 

(See also: What the U.K. Needs From Europe, and Vice Versa, from Bloomberg’s Editorial Board)