The UN Security Council on Wednesday called on the Syrian government to give "unhindered" access to hundreds of thousands of civilians trapped in the country's conflict.
A statement drawn up by Australia and Luxembourg, which includes a call for cross-border humanitarian operations, is the council's second major united decision on the war in less than a week.
The council had been deadlocked since the start of the 30-month-old uprising against President Bashar al-Assad until it passed a resolution last Friday ordering the destruction of Syria's chemical weapons.
The new statement is not legally binding like a resolution but council diplomats said it would send a strong signal to the Assad government.
The council said it is "appalled at the unacceptable and escalating level of violence" in Syria, where the UN says the war has left more than 100,000 people dead.
UN aid agencies say there are more than 2.1 million refugees outside the country, almost six million have fled their homes inside the country and they have not had access to about two million trapped civilians for several months.
The council urged both sides but "in particular the Syrian authorities" to help UN agencies and other private groups "to provide immediate humanitarian assistance to the affected people in Syria."
It called on Assad's government "to take immediate steps to facilitate the expansion of humanitarian relief operations, and lift bureaucratic impediments and other obstacles."
Aid agencies say the government has held up visas and restricted the number of foreign groups allowed to operate in Syria.
The statement says there should be "unhindered humanitarian access" across the conflict lines "and, where appropriate, across borders from neighboring countries."
The Syrian government has opposed aid missions from neighboring countries saying the supplies will go to rebel forces. Some analysts have expressed doubt that rebel groups will let aid go to government areas.
Australia's UN ambassador Gary Quinlan said the statement was "a strong unified" message from the council that humanitarian work must not be impeded.
He said there had been a "need for speed" in agreeing on a statement rather than a binding resolution because of the "terrifying" events in Syria.
UN humanitarian chief Valerie Amos has been pressing the Security Council for several months to act on the growing crisis.
Amos said after the statement was agreed that it meant more effective work could be done but that humanitarian workers in Syria have to be "protected".
"Our task now is to turn these strong words into meaningful action," Amos told reporters.
"If the commitments and practical steps in this statement are implemented, humanitarian workers will be able to reach over two million people who have been unreachable for many months," Amos told reporters.
The UN has predicted that the number of refugees in countries around Syria will increase to three million by the end of the year. Amos said aid efforts will have to be stepped up before winter arrives.
Syria's UN ambassador Bashar Jaafari welcomed the statement but said it would be up to the Damascus government now to decide how to help the UN.
UN agencies have an estimated three billion dollar funding shortfall for their Syria relief efforts and UN leader Ban Ki-moon is to hold a new conference to rally financial support in Kuwait in January, diplomats said.