He said "we've made a good start", even though the pledges would fall well short of the estimated $7 billion the U.N.is seeking.
Earlier on Wednesday, Mark Lowcock, UN Under-Secretary General for Humanitarian affairs, unveiled the same figure when he addressed a press conference alongside European Union foreign policy chief Federica Mogherini and UN Special Envoy for Syria Staffan de Mistura.
Around 80 countries, organizations, and partners are attending the donor conference in Brussels.
Lowcock earlier said he hoped to see $8bn pledged yesterday.
"The response of the world's richest countries to the conflict remains tragically inadequate - insufficient aid, not enough help for refugees and no meaningful peace process", Oxfam's Shaheen Chugtai said.
In a joint statement, a coalition of NGO said the "conference did not go almost far enough to provide adequate support to the millions of Syrians in need of assistance and who are left facing an uncertain future".
More than 700,000 people have been forced from their homes since the start of this year, as the Assad government steps up its offensive against rebel forces, intensifying the humanitarian crisis.
He stressed on importance of finding a political solution to the end the eight-year-old conflict and said that the suffering of the Syrian people was aggravated by use of chemical weapons in violation of all global laws and human principles. "Lebanon continues to be a big refugee camp".
"There would be a direct interest in Moscow as well as Tehran and I limit myself to those two capitals to identifying ways to contribute positively to a political solution", Federica Mogherini, EU Foreign Affairs Chief said.
The amount, however, plainly fell short of United Nations and European Union expectations, which co-chaired a two-day worldwide conference aimed to pump financial aid for Syrians and garner political support for UN-led Syria peace talks. They also called for the "protection" of civilians in northern Syria, where fighting in Idlib and Afrin, has created hundreds of thousands of newly displaced people. Not just for Syria, but for those border countries involved in the conflict.
"We need a political path to try and avoid Syria becoming a black hole".
In addition to the lack of funds, the United Nations special envoy for Syria, Staffan de Mistura, expressed concern that prolonged chaos would create a chance for Islamic State militants to make a comeback.