GENEVA — The United Nations appealed on Wednesday for $1.5 billion to provide life-saving aid to Syrians suffering from a "dramatically deteriorating" humanitarian situation.

The twin appeals, $519.6 million for aid within Syria and $1 billion to meet the needs of up to 1 million Syrian refugees in five countries, comprise the "largest short-term humanitarian appeal ever," the world body said in its statement.

"The magnitude of this humanitarian crisis is indisputable," said Radhouane Nouicer, U.N. regional humanitarian coordinator for Syria, who launched the appeals in Geneva.

Inside Syria, U.N. aid agencies aim to help 4 million people in need of urgent humanitarian assistance, including an estimated 2 million displaced from their homes by the fighting between President Bashar al-Assad's forces and rebels trying to topple him.

More than 525,000 Syrian refugees have already been registered and the latest estimate is that up to 1 million refugees in five countries, including Egypt for the first time, will need help in the first half of 2013, the U.N. refugee agency said.

"Unless these funds come quickly we will not be able to fully respond to the lifesaving needs of civilians who flee Syria every hour of the day — many in a truly desperate condition," UNHCR regional envoy Panos Moumtzis said.