Jordan's King Abdullah II warned in an interview published on Wednesday against allowing Syria to fracture along sectarian lines, saying a Sunni-Shiite polarisation "will have devastating consequences".
"A divided Syria means an open-ended conflict that would undermine the stability of the region and the future of its people for generations to come," the king, whose country is home to around 550,000 Syrian refugees, told London-based Asharq Alawsat Arabic daily.
"Dividing Syria is not in anyone's interest and tampering with Syria's unity is a recipe for destruction," he said.
The Jordanian monarch also warned against exporting the conflict to the wider region, saying that "fanning the fire of sectarianism in the Arab and Islamic worlds will have devastating consequences for generations to come and on the entire world."
"The sum of all fears is that the Syrian conflict could expand into a fitna (Arabic for sedition) between the region's Sunnis and Shiites."
Lebanon's Iran-backed Shiite Hezbollah movement has openly said it is fighting alongside President Bashar al-Assad's forces, while Shiite Iraqi fighters are also reported to be in Syria, supporting the regime against the mostly-Sunni rebels.
These interventions have prompted calls for a united Sunni stance against the Shiite groups involved, particularly Hezbollah.
"We are now facing a situation where both Sunnis and Shiites believe that a devastating sectarian war in Syria is inevitable," the king said.
"If we leave both sides to their conviction that what is happening in Syria is basically a jihad (holy war) in principle, the conflict and the fighting will drag on endlessly towards full destruction."
Jordan, a key US ally in the region, shares fears with the West that Muslim extremists could establish a foothold in Syria, the kingdom's northern neighbour.
"We cannot remain silent over attempts to tamper with the destiny of the region and its peoples by exploiting religion and religious schools for politics and use them as a means to divide people," he stressed, insisting on the need for a political solution that includes all sides in Syria.
The king said hosting more than half a million Syrian refugees in Jordan has placed the country "at the core" of the crisis.
"What I fear is finding ourselves in a difficult situation where, God forbid, we cannot provide relief to our brothers and sisters the Syrian refugees seeking a safe haven in Jordan," he said.
"That would mean that efforts to export the Syrian crisis have succeeded. We should not allow this, for humanitarian and political reasons. Relief efforts and support should not relapse, nor should political pressures to find an inclusive, comprehensive and political transitional solution."