The UN has appealed for a record $16 billion to fund its humanitarian operations in 2015, with almost half the total going to help victims of the Syrian conflict.
It says the money will provide aid for more than 57 million of the most vulnerable people around the world.
The UN humanitarian chief said the level of need was “unprecedented”.
The request comes as aid agencies warn they are running out of cash to fund this year’s operations in Syria.
Last week the World Food Programme announced it would have to cut food rations to Syrian refugees.
The UN is requesting $2.8 billion to help those displaced by the conflict inside Syria.
It is seeking another $4.4 billion to help more than 3,250,000 Syrian refugees registered in neighboring countries.
“The rising scale of need is outpacing our capacity to respond,” said UN Undersecretary-General for Humanitarian Affairs Valerie Amos.
“The crises in Central African Republic, Iraq, South Sudan and Syria will remain top humanitarian priorities next year.”
Valerie Amos said those conflicts accounted for more than 70% of the funding being sought.
Other major crises covered by the appeal include Afghanistan, DR Congo, Myanmar, Palestinian territories, Somalia, Sudan, Ukraine and Yemen.
However, the UN said it did not include nine countries in Africa’s Sahel region, which will be addressed in a separate request in February.
UN High Commissioner for Refugees Antonio Guterres said: “This is not business as usual in the humanitarian world. Today’s needs are at unprecedented levels, and without more support there simply is no way to respond to the humanitarian situations we’re seeing.”
Food and medical supplies for refugees have to be purchased in advance, and field hospitals have to be delivered and built.
The Kremlin announced it was working with the Red Cross on sending a humanitarian aid convoy to Ukraine and EU Commission chief Jose Manuel Barroso has told President Vladimir Putin not to carry out unilateral military action in the region under any pretext.
NATO Secretary General Anders Fogh Rasmussen has accused Russia of using humanitarian grounds as a pretext for military intervention in eastern Ukraine.
At least 1,500 people have died since Ukraine’s new government sent in troops to put down an insurrection by pro-Russia separatists in the Donetsk and Luhansk regions in mid-April.
The fighting has displaced hundreds of thousands of people, many of whom have fled to Russia.
Russia is accused of using humanitarian grounds as a pretext for military intervention in eastern Ukraine
Ukrainian forces have now encircled Donetsk, a city of one million people before the unrest began, and residents are struggling without power or reliable sources of food.
In a statement after Vladimir Putin’s conversation with Jose Manuel Barroso, the Kremlin said: “It was noted that the Russian side, in cooperation with representatives of the International Committee of the Red Cross, will send to Ukraine a humanitarian convoy.”
It did not say when the aid convoy would leave. The Red Cross acknowledged last week that it had received an offer from the Russian foreign minister about organizing aid convoys to the affected areas in Ukraine.
The Ukrainian government in Kiev and Western powers fear that a Russian humanitarian mission in the east could be used as a pretext to bring Russian military forces across the border.
In a telephone conversation with President Vladimir Putin on Monday, Jose Manuel Barroso “warned against any unilateral military actions in Ukraine, under any pretext, including humanitarian,” an EU commission statement said.
Jose Manuel Barroso made a separate telephone call to Ukrainian President Petro Poroshenko to discuss the situation in Luhansk, it added.
Hillary Clinton has arrived in Turkey for talks on the worsening crisis in neighboring Syria.
The US Secretary of State will meet Turkish leaders as well as Syrian opposition activists.
They are expected to discuss preparations for a transition of power in Syria if the government of President Bashar al-Assad falls.
The UN says there has been a surge in the number of civilians fleeing violence in Syria, especially from the northern city of Aleppo.
Turkey, like all of Syria’s neighbors, is dealing with a growing humanitarian crisis as thousands of refugees flood across the border.
Rebels in Aleppo say they are preparing a counter-attack after withdrawing from the strategic south-west district of Salah al-Din under heavy bombardment.
High on the agenda of Hillary Clinton’s talks there is how to best co-ordinate support for the fractured Syrian opposition.
Hillary Clinton has arrived in Turkey for talks on the worsening crisis in neighboring Syria
US officials say the secretary of state wants to understand Turkey’s position and its concerns as conditions in Syria deteriorate.
Hillary Clinton is also expected to announce more humanitarian aid for those fleeing the violence.
Turkey is currently supporting more than 50,000 Syrian refugees with more arriving every day.
The talks will also focus on plans for what US officials call “the day after Assad”, our correspondent says, taking steps towards a future Syria that Washington hopes will be pluralistic and democratic.
Among US concerns are reports that a growing number of al-Qaeda linked militants are fighting alongside rebels in Syria.
US intelligence officials quoted by AP news agency said at least 200 militants linked to al-Qaeda are already operating in Syria, and their numbers are growing as foreign fighters enter the country.
US officials fear they could establish a presence similar to that in Iraq, which could be hard to defeat if rebels eventually oust President Bashar al-Assad.
Analysts say it could be one reason why Washington has been reluctant to offer military assistance to the anti-Assad insurgency.
Sporadic violence was reported around Syria on Friday.
Journalists from Reuters news agency reported seeing residents fleeing Aleppo with cars packed with possessions, taking advantage of a lull in the fighting.
AFP news agency reported that a bakery in the city’s eastern Tariq al-Bab district had been hit by a shell, killing about 12 people and injuring at least 20.
State news agency Sana also reported that government forces had repelled a rebel attack on Aleppo’s international airport.
The opposition Syrian National Council said part of Aleppo’s 13th-century citadel had been damaged by shelling.
Activists also reported fighting in suburbs of the capital, Damascus.
President Bashar al-Assad is facing down stiff international pressure to step aside despite months of anti-government protests and worsening violence.
Bashar al-Assad has suffered a string of high-status defections, including his former Prime Minister Riad Hijab, who fled to Jordan earlier this week.