In an address to the Council Guterres said, “400,000 refugees have fled Syria in the last seven weeks, bringing the population of Syrians registered as refugees or waiting to be registered to 1,367,413. If current trends continue, then by the end of the year there may be up to 3.5 million Syrian refugees, together with 6.5 million people inside Syria who could become in need of help.”

“These figures are terrifying,” he said. “This is not just frightening, it risks becoming simply unsustainable. There is no way to adequately respond to the enormous humanitarian needs these figures represent. And it is difficult to imagine how a nation can endure so much suffering.”

“I know that, as High Commissioner for Refugees, I should confine my remarks to the scope of my mandate,” he added. “But as a citizen of the world, I cannot refrain from asking: Isn’t there any way to stop this fighting, to open the door for a political solution?”

Guterres told the Security Council that humanitarian funding needs had become so urgent that governments would need to look at extraordinary funding mechanisms to avoid the international response capacity becoming overwhelmed.

He also warned of the growing pressure the refugee crisis is exerting on countries in the region.

Syria has been experiencing unrest since March 2011. Many people, including large numbers of Syrian army and security personnel, have been killed in the violence.

The Syrian government says that the chaos is being orchestrated from outside the country, and there are reports that a very large number of the militants are foreign nationals.

Syrian President Bashar al-Assad has repeatedly warned the western states that they “will pay a heavy price” for supporting al-Qaeda militants against the Syrian government.