The United Nations mechanism to bring vital humanitarian aid across borders to millions of people in Syria ended Monday, after the Security Council failed to reach a vote to extend it at this stage.

The 15 members of the Security Council have been trying for days to find an understanding to extend this mechanism that allows the United Nations to deliver humanitarian aid to residents of opposition-held areas in northwestern Syria without obtaining the approval of the Syrian government.

The British Presidency of the Security Council told AFP on Monday evening that the vote, which was scheduled for Friday, was postponed to Monday and was postponed again to Tuesday morning.

Since humanitarian convoys do not cross borders at night, the operations ended Monday amid uncertainty.

And with the time difference, even if the vote is positive on Tuesday morning in New York, operations on the ground cannot resume on Tuesday morning.

Earlier Monday evening, the British ambassador to the United Nations, Barbara Woodward, who holds the Security Council presidency for the month of July, said "the key is to find an understanding".

"We want to do everything we can for the sake of the 4.1 million Syrians who are in dire need of assistance," the diplomat added.

A few days ago, Woodward denounced the use of humanitarian aid as a "bargaining chip", in an accusation targeting Russia without naming it.

The mechanism, established in 2014, allows the United Nations to deliver humanitarian aid to residents of opposition-held areas in northwestern Syria without obtaining the approval of the Syrian government, which for its part denounces this mechanism and considers it a violation of its sovereignty.

Initially, the mechanism included four border crossing points, but after years of pressure, especially from Moscow, the ally of the Syrian regime, only the Bab al-Hawa crossing remained operational, and its use period was reduced to six months, subject to renewal, which complicates planning for humanitarian activities.

According to several diplomatic sources, the decision prepared by Switzerland and Brazil, the two countries in charge of the file, provides for the renewal of the mandate for a year, as demanded by humanitarian workers.

However, Russia, which refused to extend the mandate for a year in July 2022, still insists on extending it for only six months, according to the same sources.

Switzerland and Brazil have now put forward a nine-month proposal, a diplomatic source told AFP.

And last week, UN Humanitarian Affairs Chief Martin Griffiths renewed his call to open as many crossing points as possible for at least a year.

"It is unbearable for the people of the northwest and the brave souls who come to their aid to go through these ups and downs every six months," Griffiths said, noting that aid agencies are forced each time to pre-position aid inside Syria in case the mandate is not extended.

The United Nations says that four million people in northwestern Syria, most of them women and children, need humanitarian assistance to continue after years of conflict, economic crises, disease outbreaks and increasing poverty exacerbated by the devastating February earthquake.

Although the UN mechanism has expired, at least temporarily, there are two open crossings, although they are less used as a matter of whimsy.

After the earthquake, Syrian President Bashar al-Assad allowed two more border crossings to open, but his mandate expires in mid-August.

Martin Griffiths said after his meeting with President al-Assad in Damascus at the end of June, "I have high hopes for the renewal to continue, and I see no reason to prevent that."

Since the February 6 earthquake, more than 3,700 UN aid trucks have passed through the three crossings, according to the UN. Most of them passed through the Bab al-Hawa crossing, including 79 on Mondays.