Proposals for a new settlement for the UK in the European Union will be tabled tomorrow following "good progress" in talks on David Cameron's reform demands, Donald Tusk said.
The European Council president said he would put forward the plans on Tuesday ahead of a crunch summit of EU leaders on February 18-19.
But in a sign that the Prime Minister's hopes of striking a deal could still face problems, Mr Tusk acknowledged that "outstanding issues" remained.
Downing Street has acknowledged Britain still faces "a lot of hard work" to secure an acceptable deal on EU reform and to persuade the other 27 member states to sign up to changes.
Intensive negotiations have taken place between diplomats in Brussels to finalise a package to be put to the EU's 28 national leaders in time for an early in/out referendum.
Agreement in February is regarded as crucial if the referendum is to be staged before the summer holidays.
In a message on Twitter Mr Tusk said: "Tomorrow around noon I will table proposal for a new settlement for #UKinEU. Good progress last 24 hours but still outstanding issues."