White House National Security Advisor Jake Sullivan has warned that Moscow's use of nuclear weapons in its military campaign in Ukraine would have catastrophic consequences.
A senior US official told ABC News on Sunday that Moscow's nuclear threat has not deterred the United States from helping Ukrainians defend their homeland and will not in the future.
Sullivan also said that US officials have briefed the Russians directly and privately at very high levels about the consequences of such attacks.
He said the US government has made it clear and strong that in such situations, it will respond decisively, along with its allies and partners.
When asked whether the United States would engage in a direct war with Russia, Sullivan did not give a clear answer.
However, he said the US government is planning to respond to any contingency.
Earlier, Russian President Vladimir Putin criticized Western countries for providing military assistance to Ukraine and hinted at a possible nuclear attack. Putin also authorized a new military buildup.
At this military meeting, Putin ordered the partial call-up of troops held in reserve for sudden threats to the military.
Referring to the protests by Russian civilians against Putin's decision, Sullivan said, "What the world is seeing on the streets right now is people's deep dissatisfaction with Putin's actions."
