According to the Italian news service ATI, Pope Francis was talking to children from primary schools in Rome on Monday at a special event organised by the Factory for Peace NGO.
The Holy Father said: "This is serious. Some powerful people make their living with the production of arms and sell them to one country for them to use against another country... It's the industry of death, the greed that harms us all, the desire to have more money."
The Pope addressed the pupils, saying: "The economic system orbits around money and not men, women ... So war is waged in order to defend money.
"This is why some people don't want peace: they make more money from war, although wars make money but lose lives, health, education." He quoted an elderly priest who said: "The devil enters through our wallets."
"The devil enters through greed and this is why they don't want peace."
"Peace must be built day by day and even if, one day in the future we can say that there will finally be no more wars, then too peace will be built day by day because peace is not an industrial product, it is artisanal: it is built day by day through our mutual love, our closeness.
"And in this craftsmanship, the respect for people is always at the top of the list.
"Peace, above all, is the absence of war but also joy, which day by day leads to justice, till there might be no diseased and ailing children: to do all this is to make peace; it is an action; it does not mean keeping still. It means working towards providing everybody with the solution to their problems.
"This is how peace is handcrafted."