The meeting comes just a week before the so-called 'Geneva II' peace meeting aimed at finding a political solution to the 34-month conflict that has claimed 130,000 lives.
Delegates from nearly 70 nations and 24 international organisations gathered for the one-day event chaired by UN chief Ban Ki-moon.
The meeting had gathered some USD 1.3 billion by midday as the UN sought to raise an unprecedented USD 6.5 billion.
"I am especially concerned about reports of starvation," in Syria, he said.
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The host country led the donations with a pledge for USD 500 million announced by the emir of Kuwait, Sheikh Sabah al-Ahmed al-Sabah at the opening of the conference.
US State Secretary John Kerry announced a supplementary aid package of USD 380 million, bringing the total US humanitarian aid to Syria to USD 1.7 billion.
"I am proud that the United States is the leading donor of humanitarian aid," Kerry told the conference, pointing out that "Syria's civil war is not simply Syria's problems."
Britain pledged 100 million pounds (USD 164 million), Norway USD 75 million, Denmark 26.8 million euros (USD 36.5 million)and Iraq announced an aid package of USD 13 million.
The European Union offered on Tuesday an extra 165 million euros (USD 225 million) of aid, according to EU Aid Commissioner Kristalina Georgieva, raising the union's total contributions to 2.0 billion euros (USD 2.74 billion).
"We see the humanitarian situation going from bad to worse, we have seen no improvement," Georgieva said of the conflict, which is thought to have killed more than 130,000 people.
"The continuing violence in Syria has sparked one of the biggest humanitarian crises in recent history," Amnesty International said in a statement yesterday.
"The world's response to the Syria crisis so far has been woefully inadequate," Amnesty said, ahead of the Second International Humanitarian Pledging Conference for Syria.