It may be there's long-term diplomatic leverage to be had as well in discussions on the enlargements of Nato.

BBC: Jonathan Charles in Moscow

Previous enlargements did not provoke a mass exodus to the richer countries.

ECONOMIST: A continent on the move

But if he gives too much ground to the political arguments, he risks undermining the success of this and any future enlargements.

ECONOMIST: Enlarging the European Union

There has been a failure to co-ordinate the twin enlargements.

ECONOMIST: Europe and America

Rejecting Turkish membership would probably halt other enlargements too.

ECONOMIST: Charlemagne