Pope Francis has told sick children visiting the Vatican that they could always talk to their guardian angel in times of difficulty.

The Pope made the comments during an audience with young oncology patients from Poland.

'Your journey in life is a bit difficult, dear children, because you have to get treated and overcome the disease or live with the disease. This is not easy,' he said.

He then told the children that God had given them a guardian angel so 'he may help us in life'.

'Become accustomed to talking to your angel so that he may take care of you, give you encouragement and always lead you to victory in life,' the Pope told them.

He encouraged the children, who were accompanied by their parents and healthcare specialists, not to give up because there was 'no difficulty in life that cannot be overcome'.

'Victory is different for each person; everyone prevails in his or her way, but prevailing is always the ideal, it is the horizon for moving forward. Do not get discouraged,' he said.

The exact nature of angels and how they interact with humans is a source of debate among Christians. 

John Piper wrote on his Desiring God website that the Scriptures were open to interpretation and could mean that one angel is assigned to each individual or 'that all believers have numerous angels assigned to serve them, not just one'.

Regardless of whether each saint has an individually assigned angel, he argued that the 'better' promise contained in Hebrews 1:14 was that angels are working for the good of all Christians.  Hebrews 1:14 reads: 'Are not all angels ministering spirits sent to serve those who will inherit salvation?' (NIV)

'This means that everything angels do, everywhere in the world, at all times, is for the good of Christians,' he said.

'An angel who does something by God's assignment anywhere in the world is fulfilling the promise that God will work all things for the good of all Christians — everywhere. This is a sweeping and stunning promise. All angels serve for the good of all Christians all the time. They are agents of Romans 8:28.'

The late evangelist Billy Graham also took inspiration from Hebrews 1:14 in offering a broader interpretation on the question of whether each person has an individual guardian angel. 

'Rather than only one angel, therefore, God surrounds us with a host of angels to protect us and go before us,' he said.

'Even when hard times come, Satan can never snatch us away from their protection – and some day they will escort us safely to heaven. The reality of God's angels should give us great confidence in the Bible's promises.' 

However, he cautioned people not to exalt angels above God and turn them into objects of worship. 

'While the angels are real, we are not to become preoccupied with them or to worship them,' he said. 'Only God is worthy of our worship, and only Christ saves us.'