(CNN)The idea of ending Europe's policy of open internal borders -- the so-called Schengen zone -- in favor of security measures has been "put on the table," Belgium's ambassador to the U.N. told CNN's Christiane Amanpour on Monday.
Belgian ambassador: End of border-free Europe 'on the table'
"It's definitely in the cards," Bénédicte Frankinet said. "It has been put on the table."
The Schengen policy, named for the 1985 agreement that removed borders, has come under increasingly pressure in recent months.
As hundreds of thousands of Syrian refugees seek safe harbor in Europe, several countries, including Germany, have instituted emergency border controls to process the desperate arrivals.
And in the wake of the terrorist attacks in Paris, it has become clear that several individuals known to police were able to enter Europe through Greece by posing as refugees. The attack ringleader, Abdelhamid Abaaoud -- a high-profile, known terrorist -- was able to enter re-enter Europe after leading a gruesome life in Syria, and transit all the way back to Paris.
"Of course the idea with Schengen is that we had to have the control on the external borders of Europe," Frankinet said, "and we see now that maybe that has not been the case."
"Well it just hasn't been the case," Amanpour retorted. "It's not a maybe. It hasn't been the case."
"So basically," said Frankinet, "at least for a certain time I think the issue has been brought up to the European conversation that we need to look at these issues of borders."