U.N. humanitarian chief Mark Lowcock said Wednesday that he expected donors to pledge $4.4 billion in humanitarian aid for Syria and neighbors sheltering its refugees for 2018.

Lowcock told reporters during an international donor conference on "Supporting the future of Syria and the region" in Brussels on Wednesday involving around 85 delegations that the figure was his "best guess" based on commitments made so far.

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.

Lowcock thanked the EU, Germany and the United Kingdom for making large offers.

He noted that a lot of big donors, such as the United States, have not been able to confirm their pledges for the year because of internal budget processes.

Meanwhile, speaking at the conference, Deputy Prime Minister Recep Akdağ said the international community had failed the test of sharing the burdens and responsibility with regards to the Syrian crisis.

"Indiscriminate bombing of civilian areas, forced displacement, use of chemical weapons and the attacks of terrorist organizations on civilians have caused the worst humanitarian crisis since World War II," Akdağ said. "The effects of the crisis transcend beyond the borders of Syria."

He added that Turkey hosts more than 3.5 million registered Syrians, "without any discrimination in terms of their ethnicity or beliefs."

"Free access to medical care, education and shelter have been extended to our Syrian guests," he said, adding that over 300,000 Syrian babies were born on Turkish soil since the beginning of the conflict.

"Our expenditures for the needs of Syrians in a wide range of services have reached 31 billion euros ($37.7 billion)," Akdağ said.