A major UN donors’ conference that aims to raise billions of dollars for Syria opens Tuesday in Kuwait with experts warning of a "humanitarian catastrophe" unfolding in the war-torn country.

A major UN donors' conference that aims to raise billions of dollars for Syria opens Tuesday in Kuwait with experts warning of a "humanitarian catastrophe" unfolding in the war-torn country.

The United Nations has launched an appeal to raise $8.4 billion this year, and hopes to receive major pledges at the one-day conference which will be attended by delegates from 78 nations.

UN Secretary-General Ban Ki-Moon will chair the Third International Pledging Conference for Syria, which will be opened by Kuwait's Emir Sheikh Sabah al-Ahmad al-Sabah.

"Failing to meet the required funds risks resulting in a horrifying and dangerous humanitarian catastrophe," Abdullah al-Maatuq, UN special envoy for humanitarian affairs, has said.

The conference is being held as the humanitarian situation deteriorates in Syria with many international aid agencies complaining that a shortage of funding could lead to their operations being halted.

Ahead of the meeting, around 40 international non-governmental organizations pledged $506 million, way higher than funds promised at two previous NGO conferences.

UN humanitarian affairs chief Valerie Amos said the donor response at Tuesday's conference "needs to be comprehensive".

She said the humanitarian situation had deteriorated in Syria with no reduction in violence and children particularly affected.

At the first and second conferences, also hosted by Kuwait, pledges of $1.5 billion and $2.4 billion were made. However, the United Nations has complained that not all pledges were honored.

Ban said in a report last week that devastation from the fighting in Syria had left around 7.6 million people internally displaced.

Another 3.9 million have sought refuge in neighboring countries.