Faced with an unprecedented influx of migrants, Slovenia on Tuesday called for greater European solidarity, warning it was "delusional" to expect small individual countries to handle the spiralling humanitarian crisis alone.

"Slovenia calls on the European Union states and institutions to engage actively in dealing with this disproportionate weight for our state... European solidarity is being challenged. It is delusional to expect a country of two million to (accomplish) what much larger countries haven't been able to," the government said in a statement.