UNITED NATIONS (AP) ― The U.N. Security Council unanimously approved a resolution Monday authorizing cross-border delivery of humanitarian aid to Syrians in rebel-held areas in desperate need of food and medicine, without government approval.

U.N. humanitarian chief Valerie Amos said several weeks ago that opening these routes could help 1.3 million Syrians ― and her office said Monday that if security allows, aid could reach 2.9 million people.

The resolution, a rare agreement on Syria among the often divided council, expresses “grave alarm at the significant and rapid deterioration of the humanitarian situation in Syria.” It deplores the fact that the council’s previous demands for humanitarian access “have not been heeded” by the government and opposition fighters.

The United States and many European council members said the resolution would not have been necessary if the Syrian government, especially, had complied with a February resolution demanding that all sides allow immediate access for aid.

Since February, however, President Bashar Assad has continued to bar cross-border deliveries to rebel areas and insisted that all shipments go through the capital Damascus, which has meant the overwhelming majority of aid has gone to government-controlled areas.

Monthly reports to the council since February by U.N. Secretary-General Ban Ki-moon on the resolution’s implementation have described an increasingly dire situation.

Amos told the council on June 26 that the number of Syrians in need of humanitarian assistance has increased from one million in 2011 to 10.8 million, jumping 1.5 million in just the last six months. That includes 4.7 million in hard-to-reach areas, and over 240,000 trapped in besieged areas. 

The resolution adopted Monday takes steps to overcome the Syrian government‘s opposition.

The U.N.’s most powerful body authorized U.N. agencies and aid organizations that assist them to deliver humanitarian assistance across conflict lines between government and rebel forces and through four border crossings ― two in Turkey, one in Iraq and one in Jordan without government approval. It authorizes the United Nations to monitor the loading of all aid shipments in the three countries before they cross the Syrian border.

Secretary-General Ban welcomed the adoption and called on the government, opposition forces, and all those with influence over them to ensure “unconditional humanitarian access to all people in need without discrimination, using all available routes,” lift illegal sieges, end violations of international humanitarian law, and ensure the safety of humanitarian workers, his spokesman said.

“It should never have required a Security Council resolution for a government to allow food and medicine to reach millions of families whose lives have been hanging in the balance,” U.S. Ambassador Samantha Power told the council after the vote.

“Today, we are taking steps to ensure that our resolution from February has a real impact on the ground, unlocking the impediments that stand in the way of cross-border assistance,” Power said. “The effectiveness of today‘s resolution will depend on the efforts and the cooperation of many parties, including the United Nations and humanitarian agencies.”

The resolution underscores that all 193 member states are obligated under the U.N. Charter’s Article 25 “to accept and carry out the council‘s decisions.”

It also affirms that the council “will take further measures in the event of non-compliance with this resolution” or the resolution adopted in February -- a provision that Power and other council members underscored.

The Security Council has never been able to adopt a legally binding resolution demanding an end to the conflict, now in its fourth year with over 150,000 people killed, because of insurmountable differences between Russia and China, key allies of Syrian President Bashar Assad, and the United States and its European allies, who have backed the opposition.

The council did order the elimination of Syria’s chemical weapons last September and in February it adopted a resolution focusing on the growing humanitarian crisis, not only demanding that all sides in the conflict allow immediate access for aid but calling for the lifting of sieges of populated areas, ending the deprivation of food for civilians, halting attacks against civilians including the use of barrel bombs and withdrawing foreign fighters.

Power, the U.S. ambassador, called on the council to display the unity and cooperation it showed in Monday’s vote to address “the unfinished business” in the February resolution and ensure “the end of the horrors being perpetrated against the Syrian people.”

The resolution authorizes the delivery and monitoring of aid to Syria through the Turkish border crossings at Bab al-Salam and Bab-al-Hawa, the Iraqi crossing at Al Yarubiyah and the Jordanian crossing at Al-Ramtha for 180 days. The U.N. says rebels control the Syrian side at all four crossings.