EU foreign ministers endorsed the protocol on Monday without discussion, sending it to Turkey for signing.
Ankara's top EU negotiator, Economy Minister Ali Babacan, has said Turkey will sign it as soon as it receives the document, which officials said will take about two weeks to translate into the EU's 20 official languages.
Once it has signed the accord, Ankara will have met all the conditions set by the EU for opening membership talks on 3 October.
However, the bloc must still approve a negotiating mandate for the executive European Commission, which could lead to more wrangling over Turkey's refusal to recognise Cyprus until there is a political settlement on the divided island, diplomats said.
Monday's move was a step towards reassuring Turks and financial markets that the EU expansion process remains on track despite the rejection of the bloc's constitution by French and Dutch voters partly out of hostility to further enlargement.
The 25 ministers were to debate on Monday what to say about future expansion of the bloc in a summit on Thursday and Friday.
EU president Luxembourg surprised many delegations on Friday by removing the statement on enlargement from the draft summit conclusions because of differences over how specifically to reaffirm commitments to take in Bulgaria and Romania in 2007 and open talks soon with Croatia and Turkey.