"I make a heartfelt appeal for a halt to any action that might fuel a spiral of violence with the risk of dragging the Middle East into an even greater conflict," the pope said.

The plenary indulgence for the National Eucharistic Pilgrimage is granted to anyone who participates in the pilgrimage between May 17 and July 16.

The declaration, "Dignitas Infinita" ("Infinite Dignity"), was released at the Vatican on April 8.

La declaración, "Dignitas Infinita" ("Dignidad Infinita"), se hizo pública en el Vaticano el 8 de abril.

On average, NASA -- which will hold a live online broadcast -- says about 375 years elapse between the appearance of two total eclipses in the same place.