Merkel, who has advocated having a vaguely defined partnership with Turkey, said at an event organized by her conservative Christian Democrats before the June 7 European Parliament vote that "we cannot take in everyone in Europe as a full member."

"We have to talk about the borders of this Europe," she was quoted by AP as saying. "It makes no sense if there are ever more members, and we can’t decide anything anymore," she added. 

"It is right that we say to people in the European election campaign ... our common position is: a privileged partnership for Turkey, but no full membership," Merkel said.

Turkey began EU membership negotiations in 2005, but progress has since largely ground to a halt because of disagreements over the divided island of Cyprus and strong opposition in some member countries like France, Germany and Austria. 

Neither country, however, has blocked the talks, and Germany's other main coalition party – the Social Democrats – supports EU membership for Turkey.

U.S. President Barack Obama has also urged the EU to embrace Turkey as a full member.

Sarkozy, a longtime opponent of Turkish membership, last week advocated discussing a common economic and security forum with Turkey as an alternative.

"When Angela Merkel says Europe must have borders, she is right – because a Europe without borders would be a Europe without a will, without identity, without values," he said at Sunday's event, where he was a guest of honor as France's leading conservative.

He was also quoted by AP earlier Sunday as telling Germany's Bild am Sonntag newspaper that the EU must "stop making vain promises to Turkey and study with it the creation of a big common economic and human space."

Turkey’s newly appointed foreign minister, Ahmet Davutoglu, last week said the EU must respect its past commitments, and added that "offering Turkey other alternatives than full membership is tantamount to disrespect to the bloc’s values."

Davutoglu also said Turkey must not be used as a propaganda instrument by European leaders who want to make strides in domestic politics ahead of the European Parliament elections set for June.