A report released in Beirut said the number of refugees will be 1.5 million by December, or a third of the country’s population of four million.
Some 53 percent of the Syrian refugees in Lebanon are children, the report added.
“We no longer have the capacity to carry this burden alone… We have crossed all limits,” Social Affairs Minister Rashid Derbas said at a gathering of Lebanese officials, ambassadors and the UN High Commissioner for Refugees representative, Ninette Kelley.
Lebanon currently hosts 1.1 million refugees, the highest number at 38 percent of Syrian refugees fleeing the war-torn country for other countries in the region.
The UN says Lebanon needs $1.6 billion (1.2 billion euros) for 2014 to be able to cope with the refugee crisis, but that only 23 percent of this has been gathered.
“We are really facing critical and dire challenges,” the UNHCR’s Kelley said.
“With the current level of funding… will not meet the target that we set… [to have] over 172.000 children in school next year.”
She also warned that the UNHCR “will not be able to lauch a polio vaccination campaign for all children in Lebanon under five”, should the necessary funding fail to materialize.
Kelley said 800,000 refugees will be unequipped to face winter, and 30,000 people including Lebanese will not have access to safe drinking water without the necessary financing.
“We need you to stand with us, we need you to stand with Lebanon to ensure that more funding is secured,” she said, addressing donor countries.
Also on Thursday, the United Nations launched a similar appeal in Jordan, where some 600,000 Syrians have sought refuge since war broke out in their homeland three years ago.
According to Central Bank of Lebanon statistics, the country faces a financial burden of $4.5 billion because of the refugee crisis.
In May, the International Monetary Fund said unemployment had doubled to 20 percent because of the refugee influx. It also warned growth was two percent lower than before the crisis.
Last December, the UN appealed for $6.5 billion for Syria war victims. It received $2.3 billion, and officials say the 2014 plan for the region has received just a quarter of the pledged funds.