Conservative Hungarian Prime Minister Viktor Orban, a vocal proponent of sealing borders against migration, on Friday urged Europe to build a "defence line" in the Balkans.
"I don't believe that the agreement with Turkey will be enough," Orban told the state radio.
He was referring to a deal under which the European Union will give support to Turkey in exchange for the country's implementing tighter control of its border, which last year became the main gateway for refugees and migrants hoping to reach Western Europe.
It was not about "slowing the inflow, but stopping it," said Orban, who sealed Hungary's border to all migrants between September and October.
The move eliminated his country from the so called Balkan route - from Turkey, to Greece, Macedonia and Serbia - but diverted the flow of hundreds of thousands of people to Croatia and Slovenia.
"Europe must build its new defence line on the north border of Greece," he said. Macedonia, which already filters all economic migrants arriving from Greece, "must be supported," he said.
More than 850,000 people, most of them refugees from Syria and many from Iraq and Afghanistan, reached Western Europe via the Balkan route in 2015, according to UN figures.