President Vladimir Putin's order to put Russian nuclear forces on high alert is part of a pattern of Moscow manufacturing threats to justify aggression, White House Press Secretary Jen Psaki said on Sunday.
"We've seen him do this time and time again. At no point has Russia been under threat from NATO, has Russia been under threat from Ukraine," Psaki said on ABC's "This Week" programme.
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"This is all a pattern from President Putin and we're going to stand up to it. We have the ability to defend ourselves, but we also need to call out what we're seeing here from President Putin," Psaki added.
The United States is open to providing additional assistance to Ukraine, Psaki said. Washington also has not taken sanctions targeting Russia's energy sector off the table, Psaki added.
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"We have not taken those off, but we also want to do that and make sure we're minimizing the impact on the global marketplace and do it in a united way," Psaki said.