What is Moscow threatening over the F-16 issue?

Moscow has issued so many dire warnings over the West's support for the Kyiv government that it is difficult to take the latest one seriously. Russia's deputy foreign minister Alexander Grushko has said there will be "enormous risks" if the West goes ahead and supplies Ukraine with F-16 fighter jets. Well, Zelensky has now been promised the jets, so what will Putin do? I think, and I hope I am right, that Putin has actually run out of options because pretty well everything has gone wrong for him with his "special military operation" in Ukraine. He can't stop the F-16s arriving and when the Ukrainian air force pilots have mastered how to fly them, they will begin to make a big difference in the skies over the battlefields. Putin can try and shoot them down of course but judging by Russia's total failure to win air superiority over Ukraine, it's likely that he will have little success in countering the new threat to his ambitions. Whenever Moscow threatens dire consequences, it always seems to imply that Putin will turn to unconventional weapons. But he knows, because he has received enough warnings from Nato on the subject, that if he resorts to nuclear weapons, there will be much graver consequences for Russia. Putin would face worldwide condemnation and a military response from Nato. I doubt he will take that risk. So what Mr Grushko had in his head when he issued the warning was probably more bluster than a genuine threat.