Margaret Chan, director-general of the World Health Organization, said it's urgent to find a solution to the four-year-long Syrian crisis soon, as it is now "imposing a heavy burden" on humanitarian efforts.

Chan said in Kuwait on Tuesday that the conflict, since its beginning in 2011, is "truly the biggest crisis ever recorded in the humanitarian world".

She spoke on the sidelines of the third International Humanitarian Pledging Conference for Syria.

The Middle East situation was aggravated further last year with the violent rise of the extremist Islamic State, which added complexity to what was already a chaotic situation. Global concerns over the region's stability were heightened even more with unrest in Yemen since last week.

Addressing senior officials from 78 countries and more than 40 international organizations at the conference, United Nations Secretary-General Ban Ki-moon said "regional stability is buckling" because of the four-year-old Syria crisis, and "almost 5 million Syrians are still trapped" in besieged areas.

Chan warned that her organization is seeing outbreaks of diseases among children in the region, including potentially deadly measles.

"If they are not controlled, they will cost more lives and so affect the future of children," she said.

As nearly 4 million people from Syria have sought refuge in neighboring countries, Chan said a heavy burden has been imposed on all UN agencies, including the WHO and its partners, international NGOs and local NGOs.

"Not only does it affect millions of people - women, children and men - in Syria but also all the displaced Syrians, the refugees who live in neighboring countries," she said.

Chan said the neighboring countries are suffering increasing pain as the crisis "has escalated in multiple terms" in the past four years. "This has a huge impact on the socioeconomic development of the neighboring countries," she said. "It is in the international community's interest that we, as soon as possible, find solutions."

At the Tuesday conference, His Highness Sheikh Sabah Al Ahmed Al Jaber Al Sabah, Amir of Kuwait, announced a $500 million pledge from the government and private sectors to support the Syrian people.

Chan hailed the conference, which was also attended by China's Special Envoy on Middle East Affairs Gong Xiaosheng, as "extremely timely".

"Without the help of the international community, we will not be able to provide treatments to tens of millions of patients who need healthcare - for example, to treat diabetes or hypertension, or children with cancer or those who need immunizations," Chan said.

When asked about what impressed her most when visiting those suffering in the region over the past four years, Chan said: "I think the resilience of the people in the communities is one thing that gives me a lot of hope and optimism. We need to respond to them and do our utmost."

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