Czech Republic's Prime minister Bohuslav Sobotka | John Thys/AFP via Getty Images Czech prime minister urges EU leaders to salvage Schengen Bohuslav Sobotka wants to broker a deal to preserve the passport-free zone.

The Czech prime minister wrote to fellow EU leaders Tuesday urging them to take action to save the passport-free Schengen area, which Germany's Angela Merkel has warned could be put at risk without cooperation across the region on refugees.

Czech Prime Minister Bohuslav Sobotka emailed the leaders taking part in a summit in Brussels on Thursday and Friday saying: "We must use the opportunity to ensure good prospects for Schengen during the forthcoming European Council."

"I will therefore do my utmost for our December meeting to send a clear message of our shared commitment for the future of Schengen and to provide common ground," Sobotka wrote in the letter, a copy of which was obtained by POLITICO.

He currently presides over the Visegrád group that comprises Hungary, Poland, Slovakia and the Czech Republic. Poland in particular has fiercely opposed the European Commission's proposal to create a European border guard agency that would be empowered to intervene if countries fail to take measures to secure their borders against the influx of illegal migrants.

This is one of the strategies strongly supported by Merkel for making the EU's external borders — especially the Greek border with Turkey — better guarded. An estimated 1.5 million migrants have crossed into the EU this year, many of them heading for Germany, while concerns about the effectiveness of Schengen have been heightened by the November 13 attacks in Paris.

Merkel warned at the end of August, when it began to become clear that hundreds of thousands of refugees will try to make it to Germany this year, that without a fairer allocation of migrants across the EU, "some people will want to put Schengen on the agenda." Sweden, Austria and Germany are among the countries accepting the most refugees per capita, while Eastern Europe has taken in relatively few and governments in the region have resisted pressure to accept migrant quotas.

The Schengen agreement, which came into effect in 1995, allows free travel across the borders of 26 signatory countries.

Sobotka said the priorities for this week's summit, and coming weeks, should be the efficient use of the EU border agency Frontex and the rapid implementation of the larger European Border and Coast Guard Agency, which will take over Frontex and was unveiled by the Commission on Tuesday.

He also urged action on implementing a cooperation deal with Turkey, which enlists its help in securing the EU's external borders in exchange for €3 billion in assistance for Turkey to shelter Syrian refugees on its territory.