The EU is warning Greece it faces suspension from the Schengen passport-free travel zone unless it overhauls its migration crisis response by mid-December, as frustration mounts over Athens’ reluctance to accept outside support.

Several European ministers and senior EU officials see the threat of pushing out Greece over “serious deficiencies” in border control as the only means left to persuade Alexis Tsipras, Greece’s prime minister, to deliver on his promises and take up offers of help from the EU.

If the EU follows through on its threat, it would mark the first time a country has been suspended from Schengen since it was established in 1985. The challenge to Athens comes amid a bigger rethink on tightening joint border control to ensure the survival of Schengen. The European Commission will this month propose a joint border force empowered to take charge of borders, potentially even against the will of frontline states such as Greece.