Syria's refugee crisis is approaching a "dangerous turning point" as nearly four million people face worsening conditions in exile.
UN High Commissioner for Refugees Antonio Guterres told the Security Council on Thursday "the nature of the refugee crisis is changing".
He also called for "massive international support" for countries that have opened their borders to fleeing civilians.
"As the level of despair rises, and the available protection space shrinks, we are approaching a dangerous turning point," Guterres told the 15-member council.
Close to 12 million people have been displaced by the nearly four-year war in Syria including 3.8 million who have fled to neighbouring countries such as Turkey, now the biggest refugee-hosting country in the world.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Guterres warned almost two million refugees under the age of 18, many without access to education or jobs, "risk becoming a lost generation" and more than 100,000 children born in exile could become stateless.
"If this is not addressed properly, this crisis-in-making will have huge consequences not only for the future of Syria but the whole region," he said.
The refugee chief pointed to the Kuwait donor conference on March 31 as key to helping the region cope with the overwhelming strain on services.
With Syrians increasingly taking to dangerous boat crossings, Guterres called on European governments to step up search and rescue operations in the Mediterranean.
Governments should also step forward to take in refugees with flexible visa policies, expanded family reunification, scholarships and private sponsor schemes, Guterres said.
He praised Germany and Sweden for their help and called on other countries in Europe and the Gulf to help ease the pressure on Syria's neighbours.
