U.S. Secretary of State Mike Pompeo has said that Russia and China "have blood on their hands" for vetoing a UN Security Council resolution that would have extended the delivery of cross-border humanitarian aid to war-torn Syria for a year.

Pompeo said in a December 21 statement that "there is no substitute for UN cross-border deliveries, and there are no viable alternatives to feeding millions of Syrians until the Syrian regime ceases its war on the Syrian people."

Both China and Russia used their veto powers to block the resolution on December 20. The resolution was supported by the other 13 members of the Security Council.

A Russian counterproposal to extend the provision of aid to Syria by six months failed to receive the minimum nine votes.

Russia is a close ally of Syrian President Bashar al-Assad, whose forces have been engaged in a civil war since 2011. Most of the aid would have gone to areas not controlled by Assad's forces.

Russia, which argued that the humanitarian situation in Syria had improved dramatically, has vetoed 14 Security Council resolutions regarding Syria since war broke out there.

The United Nations has been involved in the delivery of aid to millions of Syrians since 2014. The current mandate for aid deliveries runs out on January 10.

"We very much hope a solution can be found in the days ahead," UN spokesman Stephane Dujarric said on December 20.

With reporting by dpa, AP, and Reuters