Vatican: Pope Francis has warned world leaders attending the forthcoming G20 summit in Australia that they must remember their discussions will affect the lives of many people.

The Pope, in a letter to summit host Australian Prime Minister Tony Abbott, identified malnutrition, unemployment and attacks on the environment as among key areas of concern, according to a transcript on the Vatican's website on Tuesday.

Pope Francis: "It would indeed be regrettable if ... discussions were to remain purely on the level of declarations of principle." Credit:AFP

"It would indeed be regrettable if ... discussions were to remain purely on the level of declarations of principle," he wrote, in the letter dated November 6.

On current global military crises, the pontiff said "the whole world" was waiting for a co-ordinated agreement through the United Nations for a "definitive halt to the unjust aggression directed at different religious and ethnic groups, including minorities, in the Middle East".

The Pope added that it had become more and more evident that the solution to the problem could not be purely military, but must also focus on those who encourage terrorist groups through political support, the illegal oil trade or the provision of arms and technology.

The Pope also called on the world leaders, who meet in Brisbane on November 15 and 16, to give support to victims of crises, particularly refugees.

DP