In the lead up to Tuesday's donor summit in the Kuwaiti capital, the United Nations had appealed for $8.4 billion to help tackle the deteriorating humanitarian situation in Syria, where millions of people have been affected by more than four years of civil war.

"The Syrian people are victims of the worst humanitarian crisis of our time," UN Secretary-General Ban Ki-moon said in his address to the Third International Pledging Conference for Syria.

"They are not asking for sympathy, they are asking for help."

Nearly 80 governments and 40 aid agencies were represented at the gathering in Kuwait's Bayan Palace. The largest single commitment - $507 million - came from the United States. Host Kuwait pledged $500 million, the EU pledged close to $1.2 billion - double the amount the bloc offered last year- , the United Arab Emirates promised $100 million and Saudi Arabia $60 million.

'Human catastrophe'

According to UN figures, more than 200,000 people have died and more than 11 million been displaced by Syria's conflict, which was sparked by anti-government protests in 2011. Millions of refugees have since flooded into nearby countries such as Lebanon, Turkey and Jordan, posing a huge challenge to local governments.

The UN says $2.9 billion is needed in 2015 for Syrians inside their country, while around $5.5 billion is for the countries grappling to host scores of refugees.

As the proceedings got underway on Tuesday morning, UN special envoy for humanitarian affairs Abdullah al-Maatuq said failure to meet the required funds "risks resulting in a horrifying and dangerous humanitarian catastrophe."

The first donors' conference for Syria was held in Kuwait in 2013. That year the international pledges amounted to $1.5 billion, far below the $4.4 billion requested. The 2014 conference secured $2.4 billion in pledges, also falling significantly short of the $6.5 billion target.

US Ambassador to the UN Samantha Power lamented that many countries had given the same amount, or less, than they had contributed in the past.

"Years from now, when Syrians and the world look back on the country's horrific crisis, they will remember which countries stepped up to help people in dire need, and which countries did little or nothing at all," she said.

nm/jr (Reuters, AP, AFP, dpa)