GENEVA -- The United Nations presented the biggest financing appeal in its history on Friday, asking for more than $5 billion in humanitarian aid for Syria this year to help millions of people affected by the country's civil war and contain the pressures building up in neighboring countries that are overwhelmed by Syrian refugees.
"These are massive figures but they mask a human tragedy," Valerie Amos, the United Nations' humanitarian aid coordinator, told reporters after presenting the appeal to donor government representatives in Geneva. Syria's conflict, now in its third year, has set the country's development back two decades, she said. "We are concerned that as the needs are rising we are not able to meet them all."
The latest appeal for Syria equals half the financing requested by the United Nations for 16 other countries.
Calling the Syrian conflict "the most dangerous crisis since the end of the cold war," António Guterres, the United Nations high commissioner for refugees, urged world leaders to respond to the appeal not just out of compassion but as a form of "enlightened self-interest" to help stabilize the region and avert "an explosion in the Middle East."
At the United Nations headquarters in New York, the Security Council issued a rare statement critical of Syria on Friday, calling on its government to allow "immediate, safe and unhindered access" into the city of Qusayr for humanitarian assistance, particularly medical aid. Qusayr, long a rebel stronghold on the Syria-Lebanon border, fell to government forces on Wednesday after weeks of heavy fighting.
Russia, a permanent member of the Security Council and a major arms supplier to the Syrian government, routinely blocks such statements, and in fact prevented a similar one from being issued last weekend. This statement apparently passed because although the Syrian government had promised to permit relief workers into the city once it was under government control, access was still being denied.
"We expect the Syrian regime to deliver on its commitment and we need immediate humanitarian access," said Mark Lyall Grant, the British envoy to the United Nations and this month's president of the Security Council.
Also on Friday, President Vladimir V. Putin of Russia volunteered his country's troops as replacements for the Austrian members of a United Nations peacekeeping force who are vacating the disputed Golan Heights area along the Israel-Syria border, where violence from the Syrian civil war has intensified.
"Given the complicated situation in Golan Heights we could replace the Austrian contingent leaving this region, on the disengagement line between Israeli troops and the Syrian armed forces," Mr. Putin was quoted as telling newly appointed Russian officers in remarks in Moscow carried by the Interfax news agency. "But this will happen, of course, only if the regional powers show interest, and if the U.N. secretary general asks us to do so."
The departure of the Austrians, announced Thursday, has threatened the future of the Golan peacekeeping force, known as the United Nations Disengagement Observer Force, a multinational group of about 1,000 soldiers who have helped keep the area relatively tranquil for four decades. The Austrian government decided to pull its 380 soldiers on Thursday after Syrian rebels briefly seized the Austrian area of responsibility, the Quneitra crossing between Israel and Syria, in clashes with Syrian government forces that lasted for several hours.
United Nations officials declined Mr. Putin's offer. "We appreciate the consideration that the Russian Federation has given to provide troops to the Golan," said Martin Nesirky, a spokesman for Secretary General Ban Ki-moon. "However, the disengagement agreement and its protocol, which is between Syria and Israel, do not allow for the participation of permanent members of the Security Council in Undof."
The United Nations believes that one-third of Syria's 20 million people need assistance urgently and that the number could rise to 10 million by the end of the year. At the same time, relief agencies are struggling to keep up with an outflow of 200,000 refugees every month, said Mr. Guterres, the refugee commissioner. The United Nations puts the current number of refugees at 1.6 million and says that if the fighting does not stop, that number could double by the end of the year.
In response, the United Nations called for $2.9 billion in 2013 to support refugees and $1.4 billion for people trapped inside the country. It also asked for $830 million on behalf of two countries, Lebanon and Jordan, which each have more than half a million registered refugees and many more unregistered ones.
The United Nations-coordinated response has already received about $1.25 billion from appeals earlier this year, United Nations officials said.
Relief agencies working in and around Syria warn that despite the large funds provided, their ability to alleviate suffering is limited.
The influx of refugees to Lebanon has outpaced the arrival of aid, leaving many families crammed into half-built houses or squalid tents and relief agencies cutting back medical assistance, Bruno Jochum, a Switzerland-based director of Doctors Without Borders, said in an interview. "There are not enough operators on the ground delivering meaningful assistance," he said.
Deteriorating nutrition and the damage inflicted in Syria by bombardments on hospitals and water purification plants led the World Health Organization to express concerns this week about looming outbreaks of diseases like hepatitis, typhoid, cholera and dysentery.
"The needs inside Syria are so huge," Marc Lucet, emergency coordinator in Syria for Unicef, said in a telephone interview, recounting its efforts to keep water supplies and purification going and provide shelter and classrooms for children.
The World Food Program says it is now providing food for around two and a half million people, one million more than at the start of the year, and expects the number to rise to around four million by the end of 2013.
"We have reached a stage in Syria where some of the people, if they do not get food from the World Food Program, they simply do not eat," Muhannad Hadi, the program's emergency coordinator in Syria, told reporters in Geneva. "If mothers do not get food on the promised day that we deliver food, then there is nothing for them to cook for their children. Their children will go to bed on an empty stomach."
Nick Cumming-Bruce reported from Geneva, and Rick Gladstone from New York. Neil MacFarquhar contributed reporting from the United Nations.
This article originally appeared in The New York Times.