UN Secretary General Ban Ki-moon has urged the international community to foster political dialogue to alleviate the "intolerable suffering" of Syrians, as some 70 nations gathered to pledge financial support to the war-torn country.
Ban, addressing a donors' conference in London a day after peace talks on Syria in Geneva were halted by his mediator, said that process was undermined by a "sudden increase" of bombing and other military activities.
"All sides in this conflict are committing human rights abuses of a shocking scale and depravity," Ban told the UN co-hosted "Supporting Syria and the Region" event.
"There is no military solution," Ban said. "Only political dialogue - inclusive political dialogue - will rescue the Syrian people from their intolerable suffering."
British Prime Minister David Cameron urged a "new approach" to helping millions of people caught up in the conflict, focussing on education, and job creation to help Syrians rebuild their lives in the region.
Britain, the United Nations and the three other co-hosts of the conference - Germany, Norway and Kuwait - hope participants will pledge about 9 billion dollars to help 13.5 million people in Syria and 4.4 million refugees in neighbouring states.
German Chancellor Angela Merkel announced 2.3 billion euros (2.56 billion dollars) in aid over the next three years, including 1.1 billion euros in 2016, saying she wanted Thursday to be "a day of hope for the [Syrian] people."
Cameron pledged "at least an extra 1.2 billion pounds" (1.76 billion dollars) from Britain, saying "more money is needed to tackle this crisis and it is needed now."
"Our new approach of using fundraising to build stability, create jobs and provide education can have a transformational effect in the region, and create a future model for humanitarian relief," Cameron said.
"And we can provide the sense of hope needed to stop people thinking they have no option but to risk their lives on a dangerous journey to Europe."
But aid agencies and rights groups have different priorities from some of the hosts of the London meeting, warning that money alone will not address the range of problems facing millions of Syrians.
"Host countries in which refugees make up as much as a quarter of the population need vastly more donor assistance, but that money won't help Syrians who are being pushed back or driven to destitution by harsh policies," said Bill Frelick, refugee programme director at Human Rights Watch.
Part of the aid will focus on Syria's neighbouring countries of Jordan, Turkey and Lebanon, which have accepted more than 4 million Syrian refugees between them.
"Today, one of every five people living in our kingdom is a Syrian refugee," Jordan's King Abdullah said, adding that the government spends about a quarter of its national budget on refugees.
"We have reached our limit," he said. "Our country will continue to do what we can do ... but it cannot be at the expense of our own people's welfare."
The United States promised about 600 million dollars in additional aid, plus 290 million dollars for the education of refugee children in Jordan and Lebanon.
Save the Children said educational provision is vital to avoid many of the estimated 5.8 million children displaced by the conflict becoming a "lost generation," with about half of them currently out of school.
"We cannot stand by and accept that we may see a lost generation of children who have never had the chance to go to school," said Tanya Steele, Save the Children's chief executive.
Norway pledged 2.4 billion kroner (288 million dollars) for this year, with Foreign Minister Borge Brende saying the "humanitarian needs are immense."
"Norway has never given so much money to a humanitarian crisis of this kind before," he said.