The U.S. slammed Russia and China's veto decision to block a U.N. Security Council resolution that would have extended cross-border humanitarian aid to four million Syrians for another year.

U.S. Secretary of State Mike Pompeo said in a statement on Saturday, "The Russian Federation's and China's veto yesterday of a Security Council resolution that allows for humanitarian aid to reach millions of Syrians is shameful."

"To Russia and China, who have chosen to make a political statement by opposing this resolution, you have blood on your hands," he added.

Humanitarian aid currently flows into Syria through U.N.-designated checkpoints in Turkey and Iraq without the formal permission of the Syrian regime in Damascus, but that authority is due to expire on Jan. 10.

On Friday, Russia, backed by China, cast its 14th U.N. Security Council veto since the start of the Syrian conflict in 2011 to block cross-border aid deliveries from Turkey and Iraq to millions of Syrian civilians.

The resolution drafted by Belgium, Kuwait and Germany would have allowed cross-border humanitarian deliveries for another year from two points in Turkey and one in Iraq. But Syrian regime ally Russia only wanted to approve the two Turkish crossings for six months.

Russia and China vetoed the draft resolution. The remaining 13 members of the Security Council voted in favor.

Since 2014, the Security Council has sent aid through four border crossings — Bab al-Salam and Bab al-Hawa in Turkey, Al Yarubiyah in Iraq, and Al-Ramtha in Jordan.

The sponsors of this year's aid resolution circulated a draft that has been discussed for several weeks that would add a new crossing point in Turkey and extend cross-border operations for a year.

Russia and China, which are allies of Assad regime, circulated a rival resolution Monday that seeks to close the crossing points in Iraq and Jordan, leaving only two in Turkey while not adding the third proposed in the rival resolution. And it would renew the cross-border operation for only six months.

Last year, Russia and China abstained in the 13-0 vote authorizing the crossing points.

Russia's ambassador to the United Nations, Vassily Nebenzia, said the latest resolution was "obsolete" because the authorities in Damascus had "retaken control of most" of Syria's territory.

But the U.N. humanitarian relief department says the aid remains crucial as the situation on the ground has deteriorated and Syria is heading into winter.

Four million Syrians directly benefit from the cross-border aid shipments.

"I am in a state of shock," Kelly Craft, the U.S. ambassador, said after the Russian and Chinese vetoes. "I am deeply and profoundly disappointed."

British envoy Karen Pierce said the Russian veto showed "breathtaking hypocrisy" by Moscow.

The resolution failed just as tens of thousands of civilians have been fleeing the northwestern Idlib region amid heavy bombardments by the regime forces backed by Russia.