Russia blocks US-drafted UN resolution to renew international inquiry into who is to blame for chemical weapons attacks in Syria.
It was the 10th time that Moscow has used its veto power to stop council action that targeted its ally Assad regime.
The Joint Investigative Mechanism has to cease operations as its current mandate expires at midnight Thursday.
U.S. President Donald Trump pressed earlier for the extension of the mandate, saying on Twitter he needs "all" on the council to renew the so-called JIM "to ensure that Assad Regime does not commit mass murder with chemical weapons ever again."
Russia has been seeking changes in the way the JIM operates. Syria accepted a Russian proposal in 2013 to relinquish its chemical weapons stockpile.