German Chancellor Angela Merkel is warning against shipping weapons to Syrian rebels fighting to overthrow President Bashar Assad.

The German leader told Parliament on Thursday that she understands why Britain, France and the United States are considering arms deliveries to some rebel groups in Syria, who are facing strong resistance from Syrian government forces and its Hezbollah allies.

But Merkel said that in her view, "the risks would be incalculable."

She did not explain why but critics fear Western arms would only prolong the conflict without tipping the scales decisively. And Western weapons including anti-aircraft missiles could fall into the hands of Islamic extremists who might use them against Western interests someday.