Pope Francis on Wednesday issued a fresh call for peace through negotiation as he deplored the bloody conflicts in Ukraine and Gaza, and once again limited his public speaking at his weekly audience in St Peter's Square due to lingering health issues.

"We should never forget that war is always a defeat, we cannot continue in war, we should make all efforts to mediate, to negotiate an end to the war, let's pray for this," the pontiff said in brief remarks at the end of the audience, citing "martyred" Ukraine and the Israeli-Palestinian conflict.

The 87-year-old Francis, who has mobility problems and has been suffering in recent weeks from colds and bouts of bronchitis, once again skipped reading most of his pre-prepared texts for the audience.

He delegated the task to an aide, telling the faithful he was still forced to limit his public speaking.

Earlier this month, Francis caused controversy by suggesting in an interview with Swiss broadcaster RSI that Ukraine should "show the courage of the white flag" and open talks with Russia.

His deputy, Cardinal Pietro Parolin, later clarified Russia should first halt its aggression.