UNITED NATIONS - Nearly 1.3 million Syrians are now either registered as refugees or being assisted in Syria's neighboring countries and North Africa, deputy UN spokesman Eduardo del Buey told reporters here Wednesday.

"More than half of the current refugees have left Syria over the last three months, with the UN Refugee Agency (UNHCR) having registered about 7,000 people on average per day for the past four weeks," del Buey said at a daily news briefing here.

Syrian refugees are seen as UN High Commissioner for Refugees (UNHCR) Antonio Guterres visits Al Zaatri refugee camp in the Jordanian city of Mafraq, near the border with Syria March 13, 2013. [Photo/Agencies]

"To enhance assistance delivery and preparedness, humanitarian agencies are revising the response and contingency plans," he said.

The Syria Humanitarian Assistance Response Plan (SHARP), covering the period from January to June 2013, requires $519 million in funding, he said. "But as of 7 April, according to the Office for the Coordination of Humanitarian Affairs (OCHA), the plan was only 40 percent funded."

"All sectors are underfunded, especially community services, health, education and shelter and non-food items," he said. "The water, sanitation and hygiene sector has received only 7.5 percent of its required funding, just as the hot summer season is approaching and the threat of water-borne diseases is on the rise. "

"So far, donors have committed more than $400 million of the money pledged in Kuwait, leaving about $1.1 billion uncommitted," he said.

The Syrian crisis, which broke out in March 2011, and subsequent violence have prompted a massive influx of Syrian refugees into neighboring countries, such as Lebanon, Turkey and Jordan.

Asked about the shortfall in funding the appeal, del Buey said that UN Secretary-General Ban Ki-moon "has been calling world leaders trying to ensure that the money that has been pledged is made available".

Asked about the situation in Syria, he said that "the secretary-general has called for all sides to lay down their arms and engage in peaceful negotiations."

Asked about the Syrian government's communications on chemical weapons allegations, he added afterward that the United Nations has received a letter from the Syrian government concerning the work of the technical mission. "That letter is being studied," he said, without elaborating.

The Syrian government has formally asked for a UN probe into the armed rebels' alleged use of chemical weapons in the attacks last month. But the armed opposition denied the charges.

The secretary-general, while in Rome, on Tuesday called on Damascus to "extend its full cooperation" with the UN investigators and "to allow the (UN technical) mission to proceed".

The United Nations said late last month that Syria has accepted the head of the United Nations investigation into allegations of reported chemical weapons use in Syria, Ake Seelstrom, a Swedish scientist, who was appointed in late March by the secretary- general.

At least 25 people were killed and 130 others wounded last month when armed men fired a rocket stuffed with chemical materials at the Khan al-Asal town in Aleppo, Syrian state-media said, accusing the armed opposition fighters of being behind it. However, the rebels denied the accusations and turned the accusation finger against the government.