Nick Schifrin reports in tweets that Vladimir Putin has issued orders to invade Ukraine.
What could be the last chance to avoid war would be to reopen that last exit ramp for Putin.
At this point, only President Joe Biden has a shot at doing that successfully.
Summary and Conclusion

In conclusion, Biden should act urgently to reopen the last off-ramp, as suggested above, and even propose a summit with Putin, and perhaps other leaders.
At the same time, Biden should take the two steps in the United Nations suggested above.