This is an escalation that looks like it was intended to signal nuclear readiness and that their nuclear saber rattling isn't a joke.
The US claims this didn't happen. Russia hasn't said either way.
Ukraine could escalate in retaliation. But I don't think there is any escalation path they can take that would move them into a stronger negotiating position without Russia simply responding much more forcefully.
?itok=8cjEIrGD