The Greek Orthodox Church is urging Christians across Europe to unite in an appeal against a ban on crucifixes in classrooms in Italy.
The European Court of Human Rights in Strasbourg ruled last week that the presence of crucifixes violated a child's right to freedom of religion.
Greece's Orthodox Church fears the Italian case will set a precedent.
It has called an emergency Holy Synod meeting for next week to devise an action plan.
Although the Greek Orthodox Church has been at odds with Roman Catholicism for 1,000 years, the judicial threat to Christian symbols has acted as a unifying force.
The European Court of Human Rights found that the compulsory display of crucifixes violated parents' rights to educate their children as they saw fit and restricted the right of children to believe or not to believe.
The head of the Greek Church, Archbishop Ieronymos, shares Catholic complaints that the court is ignoring the role of Christianity in forming Europe's identity.
One of his subordinates, Bishop Nicholas from central Greece, lamented that at this rate youngsters will not have any worthy symbols at all to inspire and protect them.
Football and pop idols are very poor substitutes, he said.
The Greek Church has ostensibly intervened in this case in response to an appeal by a Greek mother whose son is studying in Italy.
But without doubt it is concerned that its omnipotence in Greece is under threat.
A human rights group called Helsinki Monitor is seeking to use the Italian case as a precedent.
It has demanded that Greek courts remove icons of Jesus Christ from above the judge's bench and that the gospel no longer be used for swearing oaths in the witness box.
Helsinki Monitor is urging trade unions to challenge the presence of religious symbols in Greek schools.
The socialist government here is also considering imposing new taxes on the Church's vast fortune, but at the same time is urging it to do more to help immigrants and poor Greeks.