The head of the Catholic Church has said it may consider ordaining married men to cope with a shortage of priests.

While saying "optional celibacy" is not the solution, Pope Francis expressed an openness to studying whether so-called "viri probati" could be ordained.

Viri probati is a Latin term for 'tested men', or married men of proven faith.

He told the German weekly newspaper Die Zeit: "We must think about whether viri probati are a possibility.

"Then we have to decide what tasks they can take on, for example in remote communities."

It is thought the option could allow men who are already married to be ordained as priests.

However, single men who are already priests would not be allowed to marry.

The same rite already allows some married non-Catholic clergymen who become Catholics to be ordained priests - such as former Anglican clergy.

In the same interview, the Pope also spoke of his own faith.

 "I too know moments of emptiness", he said, while also speaking about "spiritual dark moments" in his life.

Asked about how the faithful can help when people experience crises, he said: "One cannot grow without crises: in human life, the same thing happens.

"Even biological growth is a crisis...The crisis of a child who becomes an adult. And faith is the same."

He also spoke again about what he has called the "Third World War" - drawing attention to conflicts in Africa, Ukraine, Asia and Iraq.

The conversation ended with Pope Francis confirming plans to visit India, Bangladesh, Colombia and Portugal.