It's not the first time since 2014, and saber-rattling only works if you first pose a credible threat to invade.
This is a really good move, by the way:
Today, after weeks of close consultation with Ukraine and partners on the Security Council, the United States called an open meeting of the Security Council to discuss a matter of crucial importance to international peace and security: Russia’s threatening behavior against Ukraine and the...
usun.usmission.gov
This risked catching some blame for provocation should Moscow invade over the weekend, but their return rhetoric (dismissing this as a stunt) undermines that. If they do invade, then obviously it wasn't a stunt. The rhetoric therefore tends to imply that they won't invade until after the meeting.
It will be
very interesting to see how Putin plays this one on Monday. If he publicly commits to diplomacy, then invades, that's hard to walk back. That puts Biden in a position to mend fences within NATO afterwards, because Moscow will very obviously be both a threat and untrustworthy.
If Putin ultimately backs down after the meeting, Biden gets the credit. He looks strong, having defused the threat likely without making concessions, and diplomacy comes off looking like it works. This also would make extortion via saber-rattling harder in the future.
Biden has been proving in the last six months to be shrewder than expected, looking more like Bush 41 than Bush 43. Like Bush 41, he's also a gaffe machine, but we've known that for decades. The latter, interacted with inflation, appears to have lost him the media war and by extension the public opinion battle. I doubt that this can flip that script, but it's a good start.