US National Security Advisor Jake Sullivan says the emergence of alleged atrocities in formerly Russian-occupied areas of Ukraine amount to "war crimes," but adds that the situation in the country has not risen at the moment "to the level of a genocide." During a press briefing at the White House, he also warns that "the next stage of this conflict may very well be protracted." (COMPLETES VIDI327P36R_EN, VIDI327P38G_EN & VIDI327P2VF_EN) IMAGES AND SOUNDBITES