BEIRUT (AP) — An impasse at the United Nations over a border crossing with Syria's last rebel-held enclave is putting 4.1 million Syrian there in danger, the president of the International Rescue Committee warned this week.

David Miliband’s comments came more than two weeks after the U.N. Security Council failed to renew the mandate for the Bab al-Hawa border crossing between Syria and Turkey, which secures aid for Syrians in the enclave.

The vast majority of people in northwestern Syria live in poverty and rely on aid to survive — a crisis that was further worsened by a devastating magnitude 7.8 earthquake that hit southern Turkey and northern Syria in February. The earthquake killed more than 50,000 people, including over 6,000 in Syria, according to the United Nations. The quake also displaced hundreds of thousands of others.

“The people of northwest Syria can ill afford a new wave of suffering, having lived through the trauma of the earthquake,” Miliband told The Associated Press in an interview on Tuesday.

He urged the Security Council to “do its job” and resume the humanitarian border crossing.

The council earlier in July failed to adopt one of two rival resolutions on the crossing. Russia, a top ally of the Syrian government in Damascus, vetoed a Swiss-Brazilian compromise resolution backed by Western countries that renewed authorization for the crossing of aid through Bab al-Hawa for six months. Moscow’s draft resolution with additional requirements — including increasing aid delivery to the opposition enclave through Damascus — only received China’s backing.

The paralysis also comes as donor fatigue has led to aid cuts in aid to both northwestern Syria and neighboring countries hosting millions of Syrian refugees who fled the ongoing conflict, now in its 13th year.

Syrian President Bashar Assad opened two additional crossing points from Turkey at Bab al-Salameh and al-Rai to increase the aid flow to the quake victims. The U.N. says that some 85% of its aid to northwestern Syria goes through Bab al-Hawa, a more efficient route.

For the moment, Miliband said the International Rescue Committee is trying to cope by using other crossings and finding other ways of getting aid into the enclave.

“Our point of view is that interference with the humanitarian crossing point poses severe danger to the efficiency and the effectiveness of humanitarian aid,” he explained.

Additionally, the United States said Monday that it has joined major donors in demanding the U.N. be able to deliver aid through Bab al-Hawa independently and to everyone in need — a rejection of conditions set by Syria and backed by its ally Russia that Damascus control all aid and banning U.N. communications with rebels in the region.

The Security Council initially authorized aid deliveries in 2014 from Turkey, Iraq and Jordan through four border crossing points into rebel-held areas in Syria.

However, Russia, backed by China, over the years successfully applied pressure to reduce the authorized crossings to just Bab al-Hawa, and the mandates from a year to six months.

Moscow alleges that militant groups in the northwestern province of Idlib are taking the aid and preventing it from reaching families in need. Russia and China have been calling for all aid to be routed through Damascus instead.

But Syrians in the northwestern enclave, as well as Western countries critical of Assad, say they are skeptical of the push.

“There’s a lot of danger for people in need in northwest Syria,” Miliband said. “And it’s very important that they’re not forgotten.”