The fate of a Western and Arab-backed United Nations resolution demanding immediate access everywhere in Syria to deliver desperately needed humanitarian aid rests with Russia.

Diplomats said it was unclear whether Russia will veto the resolution, support it or abstain. Whatever it decides, close ally China will almost certainly follow suit.

The supporters scheduled a Security Council vote Saturday morning, giving Russia's UN Ambassador Vitaly Churkin the extra time he requested to get instructions from Moscow.

US Ambassador Samantha Power expressed strong support for the resolution on Friday and urged the council to "speak with one voice to help ensure that the children, women and men affected by the Syrian crisis receive the essential life-saving assistance they are being denied."