Washington considers that it bears the responsibility "to try and avoid the complete and total destruction of Syria", fearing the potential fallout across the region and a possible surge in migration, Kerry said on a stop in Madrid.
Climate change fans global security crisis, Kerry
"We have a moral interest to try and stop this unfolding catastrophe," he said. "The threat of many more (refugees) coming if the violence continues and Syria absolutely implodes is real."
Kerry also said he feared the consequences of Russia's air strikes in Syria.
"Our fear (is that)... Russia is simply there to prop up (President Bashar al-) Assad," he said, warning that Moscow's air campaign might "attract more jihadists to the fight".
Kerry to meet Netanyahu, Abbas on Palestinian-Israeli unrest this week
If Moscow is willing to "help us find a political solution as well as... fight Daesh, then there is a possibility to try to find a way to another path", he said, using an Arabic acronym for the Islamic State extremist group.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ