Aid deliveries to millions of Syrian civilians were hanging in the balance on Thursday ahead of the expiration of a United Nations mandate authorizing cross-border humanitarian convoys from Jordan, Turkey and Iraq.

UN spokesman Stephane Dujarric urged the 15-member Security Council to break its deadlock and renew authorization of cross-border deliveries of supplies to some 4 million Syrians in areas beyond the control of Damascus.

“We very much hope that members of the Security Council will come together and agree on some type of resolution which will allow continued cross-border deliveries of humanitarian aid,” Dujarric told reporters on Thursday.

“The situation in the northwest and the northeast of Syria is critical. Every day we talk about the increased humanitarian suffering. It would be that much worse if we would not have access through cross-border operations.”

Since 2014, the council has authorized aid convoys through four crossings — Bab al-Salam and Bab al-Hawa in Turkey, Al Yarubiyah in Iraq, and Al-Ramtha in Jordan — but the mandate for these operations expires on Jan. 10.

Last month, Russia and China vetoed a draft resolution renewing the mandate of cross-border supplies, with members arguing over how many crossings should remain open, and for how long.

Dujarric warned that the clock is ticking and that, without a deal, millions of civilians would be left in the lurch.

“We’re always making contingency plans, but the loss of the cross border will make it that much more difficult for the U.N. and its humanitarian partners to reach millions of Syrians who need access to life-saving aid,” Dujarric said in New York.

On Wednesday, David Miliband, president and CEO of the International Rescue Committee, which provides aid to some 1 million civilians across Syria, called the cross-border convoys a “linchpin” of humanitarian operations in the war-ravaged country.

“As needs intensify in Idlib and across northeast Syria, and as tensions escalate dangerously throughout the Middle East, it is vital for the Security Council to step up its commitment to Syrians in need,” Miliband said in a statement.

“The last thing the region needs is for the delivery of humanitarian aid to be compromised at such a critical time.”