Archbishop Silvano Tomasi said officials should take action "though the mechanisms of the United Nations."
He was repeating the call of Pope Francis and told Vatican Radio the Holy See wanted to urge the world to act to stop the violence against religious minorities and find safety for refuges already forced from their homes.
The United Nations estimates that 50,000 Christians have been displaced by the extremist group Islamic State (I.S.), formerly ISIS.
I.S. has been taking over large parts of Iraq forcing Christians to convert to Islam, pay a tax or face death.
Archbishop Tomasi said: "In this tragic context of violence, the Church 's job is difficult but continuous.
"The example of the Holy Father is clear: he continues to appeal to the international community and to all of us believers, to pray that the path to peace will be found, inviting everyone to negotiate and inviting the countries that are capable of stopping the aggressor.
"Local bishops, the Patriarchs, Orthodox and Catholics of various rites – the Syriac, Chaldean, Melkite – met a few days ago and clearly formulated important plans of action.
"First, to ask for help from the international community to stop the violence and the killing not only of the Christians but also of the Yazidis and other groups.
"We think that Christians are being decapitated and from the photos, you can see the heads are put on hooks like wall or gate decorations. These things are unheard of, truly unacceptable!
"Second, they ask that there is an international presence that guarantees the return of the Christians to their villages and to their homes.
"It is not right that the international community accepts that automatically, the Christians are condemned to exile.
"They have the right to live at home, where they've lived for 1,700 years, since before the arrival of Islam, so that they can continue not only because it is their natural right, but also because they are a presence that is a benefit to the Islamic community and which helps diversify the social context which can slowly favour a democracy that respects the identity of every person and each group."