Pope Benedict XVI said he is convinced peace will prevail in 2013, despite the inequality, terrorism and "unregulated financial capitalism" that afflict the world today.
Benedict celebrated a Mass in St Peter's Basilica in the Vatican to mark the Church's world day of peace.
In the front pews were diplomats accredited to the Holy See, who will next week attend the Pope's annual address about the plight of the world's poor and its war-torn regions.
In his homily, Benedict said despite today's terrorism, criminality and the inequality between rich and poor, he was convinced the "numerous works of peace, of which the world is rich, are testimony to the innate vocation of humanity to peace".
Later, a man scaled the scaffolding around St Peter's Square in the Vatican and draped a banner calling on Pope Benedict XVI to "Stop Terrorism".
The man identified himself on the banner as Julian Jungarean, a Romanian who has previously scaled the colonnade around the piazza.
Witnesses said uniformed officers were speaking with him from the ground and a nearby roof.
Jungarean's protest did not appear to cause the Pope any disturbance.