European Council President Donald Tusk speaks during a joint news conference with Bulgaria's President Rumen Radev in Sofia, Bulgaria April 4, 2017. REUTERS/Stoyan Nenov

SOFIA (Reuters) - The European Union is determined to stick to a deal with Turkey to stem the flow of undocumented migrants into the bloc, European Council President Donald Tusk said on Tuesday.

Tusk, who met Bulgaria’s President Rumen Radev, welcomed Sofia’s efforts to boost security on its southeastern border with Turkey to prevent migrants from crossing. He said Brussels would provide additional financing if the situation worsened.

“We are determined to keep routes of illegal migration in this region closed,” Tusk told reporters. “We remain committed to the full implementation of the EU-Turkey statement.

“The EU is honoring its commitments, just like we expect Turkey to continue keeping its part of the deal.”

The EU-Ankara agreement came into force in March 2016 after more than a million refugees and migrants from Syria, Iraq, Afghanistan and beyond reached Europe in 2015, many crossing to Greek islands from Turkey.

“Should further difficulties arise on Bulgaria’s borders, the EU has already planned emergency funding, and stands ready to react quickly in support of Bulgaria,” Tusk said.

Turkey has said it may cancel the migrant readmission agreement, under which it takes back people who enter Greece through irregular routes. It was angered after several EU states prevented Turkish politicians from holding rallies to drum up support for plans to give President Tayyip Erdogan new powers in a referendum.

Bulgaria, the EU’s poorest member, expressed concern about a possible new migrant influx given that Turkey-EU tensions are running high.

“It is extremely important for us to develop good neighborly relations with Turkey,” Radev said. “At the same time, rising tensions between the EU and Turkey create the greatest risk for Bulgaria.”