The European Commission will resist pressure from France and others to draw final borders for the European Union when it publishes a sensitive report this week on the bloc's capacity to absorb further members.
EU leaders, under pressure from France and Austria, where public opposition to Turkey's candidacy is strongest, instructed the Brussels executive in June to prepare a definition of the Union's "absorption capacity" for a summit next month.
The focus on "absorption capacity" has become a coded way of questioning whether the EU will ever be able to absorb such a large, poor, populous and overwhelmingly Muslim country as Turkey, extending the bloc's borders to Iran, Iraq and Syria.
The study will accompany a critical report on Turkey's progress in the year since it began membership talks, which EU sources say will lament a slowdown in the pace of reforms and a failure to open its ports to shipping from Cyprus.
The Commission will argue on Wednesday that Europe's frontiers are "defined more by values than by firm geographical borders," according to a source familiar with the report.
"It's not possible to take a pen and draw final borders," the source said.
Conservative French presidential frontrunner Nicolas Sarkozy called in a recent speech in Brussels for the EU to spell out its ultimate borders.
He argued the EU should offer an intermediate status, which he calls a "privileged partnership", to countries such as Turkey or North African countries which in his view should never join.