The Greek ambassador returned to Austria on Wednesday, formally ending strains that began after the shut-down of the migrant route to central Europe left tens of thousands of people stranded in Greece.

The closing of the West Balkans route was orchestrated in Austria, and Greece reacted by pulling its ambassador back to Athens in late February. For weeks, chaos ruled on Greece's western border, as many of the nearly 55,000 migrants in the country tried to push into Macedonia, the first stop on the now-closed Western Balkans route.

The crisis has eased, with arrivals dropping since Greece started returning people arriving clandestinely from Turkey under a March deal with the EU. But Austrian Foreign Minister Sebastian Kurz warned against complacency, suggesting that Ankara could exploit the agreement to press for concessions the EU may be unwilling to make.

"Even if there is a certain easing, the Turkey deal in particular is something where we have to be careful that we do not fall into dependency" on Ankara, he said at a news conference with Greek counterpart Nikos Kotzias. Kotzias flew into Vienna on an official visit early Wednesday, accompanied by returning Ambassador Chryssoula Aliferi.

Austria earlier this year swung from an open-door migrant policy to imposing strict restrictions. While the country still backs EU-wide migrant quotas, Kurz expressed understanding for the opposition among some states to such quotas.

With "differing concepts in the refugee question," one priority must be ending open border policies and focusing instead on financing and organizing aid to front-line states to the Middle East conflict zones, Kurz said. This, he said, could lead to a possible rethink of quotas by countries now opposed because they see no end to the influx.

"The most important point is reducing the inflow, creating a normal situation," he said. "I believe that then we then will also be more capable of acting in the search for a common European solution."

Kotzias suggested that the EU itself was to blame for the lack of unity, criticizing perceived inaction in failing to develop a common strategy at the outset of the migrant crisis despite his country's warnings that thousands were arriving daily.

And he urged the more than 10,000 migrants still camped out at the main Idomeni crossing to Macedonia not to believe "actors and foreign NGOs" claiming that the West Balkan route will reopen."

"They lie," he said. "The borders are closed."