Vatican City, Jan 1- Pope Benedict XVI today urged world leaders to defend Christians against abuse and intolerance after a New Year's day bomb attack in a Coptic church in Egypt claimed 21 lives.

In the wake of mounting tensions and "especially discrimination, abuse and religious intolerance which are today striking Christians in particular, I once again launch a pressing appeal not to give in to discouragement and resignation," he said, speaking at the New Year mass.

He appealed for the "concrete and constant engagement of leaders of nations," in what he termed a "difficult mission."

The pontiff underscored that "humanity cannot display resignation in the face of negative forces of selfishness and violence, it cannot get accustomed to conflicts which claim victims and endanger the future of people."

The attack in Alexandria also wounded 43 people.