World Humanitarian Summit opens in Istanbul to tackle crisis

Jan Eliasson, UN Deputy Secretary-General, talks to members of the media during a news conference ahead of the World Humanitarian Summit, in Istanbul, Sunday, May 22, 2016. World leaders and representatives of humanitarian organizations from across the globe converge in Istanbul on May 23-24, 2016 for the first World Humanitarian Summit, focused on how to reform a system many judge broken. (AP Photo/Lefteris Pitarakis) (The Associated Press)

Jan Eliasson, right, UN Deputy Secretary-General, and Stephen O'Brien, left, UN Under-Secretary-General for Humanitarian Affairs listen to a question during a news conference ahead of the World Humanitarian Summit, in Istanbul, Sunday, May 22, 2016. World leaders and representatives of humanitarian organizations from across the globe converge in Istanbul on May 23-24, 2016 for the first World Humanitarian Summit, focused on how to reform a system many judge broken. (AP Photo/Lefteris Pitarakis) (The Associated Press)

Jan Eliasson, right, UN Deputy Secretary-General, talks as Stephen O'Brien, left, UN Under-Secretary-General for Humanitarian Affairs, looks on during a news conference ahead of the World Humanitarian Summit, in Istanbul, Sunday, May 22, 2016. World leaders and representatives of humanitarian organisations from across the globe converge in Istanbul on May 23-24, 2016 for the first World Humanitarian Summit, focused on how to reform a system many judge broken. (AP Photo/Lefteris Pitarakis) (The Associated Press)

An unprecedented summit to revamp humanitarian aid and global responses to modern-day crises has opened in Turkey.

The first World Humanitarian Summit is being convened in Istanbul on Monday and Tuesday in a bid to better tackle what the United Nations describes as the worst humanitarian crisis since World War II.

The gathering was conceived four years ago by U.N. Secretary General Ban Ki-moon. In preparation, 23,000 people were consulted in over 150 countries, U.N. officials say.

The U.N. under-secretary general for humanitarian affairs and emergency relief coordinator, Stephen O'Brien, said the summit's success would be defined not by funds raised but by the number of commitments to action made.

He said the summit is "a once in a generation opportunity to set in motion an ambitious and far-reaching agenda."