Every time Vladimir Putin makes a threat, it seems President Biden and his minions immediately look for a desk to crawl under. 

The Russian strongman saber-rattles about nuclear weapons and the administration responds, “Oh no, we’ll never do anything to offend you.” 

You know what, though, America has a very strong nuclear force and a very strong missile defense system — one that, by the way, was started four decades ago by my former boss, President Reagan.

It would be nice if, just once, Mr. Biden said America has the nuclear force to destroy Russia, and that Mr. Putin ought not to forget that. Just once, blast back. 

Or how about a reminder that the entire Russian economy is only 6.5 percent the size of the American economy, and now that America’s belated sanctions are starting to take hold, we’re ruining Russia’s foreign exchange reserves and their currency, essentially closing down their banks and doing great damage to their energy sector. We could even do much more in those areas.

It takes 120 rubles to buy a dollar, which is pathetic. Actually, if you live in Russia, it probably takes 200 rubles to buy a dollar. Even more pathetic. 

So Mr. Biden ought to really start acting like an American-first president instead of cowering at every Putin statement.

NATO forces and their economies are so vastly, overwhelmingly larger and more powerful than anything Russia could possibly muster. 

While nothing’s perfect in life, America and NATO show the great virtues of democracy and a market economy.

Mr. Putin’s Russia shows the weakness of an authoritarian, undemocratic, state-controlled economy. In the long run, Mr. Putin and his phantasmagorical, ahistorical dreams of a tsarist Russian empire will ultimately be doomed to the dustbin of history. He knows it. Most people know it. Why doesn’t Joe Biden know it?

Stop cowering, Mr. Biden. Start acting like the leader of the greatest country in the history of history. You should’ve slapped the sanctions on before Mr. Putin invaded. 

You told us withholding the sanctions would be a deterrent. You were wrong. That deterred nothing. Then you turned around and said they were never meant to be a deterrent. Really?

What are you talking about? Under pressure from Congress, you finally got around to putting a stop to Russian oil imports and ponied up $15 billion of additional assistance to Ukraine. You should’ve delivered weapons and money at the beginning of Mr. Putin’s adventurism, not after it was too late. 

I don’t live and die by the polls, but it’s clear the country wants Mr. Biden to stop leading from behind.

From CBS-YouGov: 52 percent say America has not been strong enough toward Russia, with 36 percent saying we’ve been about right. Strongest options against Russia: 65 percent say tougher economic sanctions — that means all of their fossil fuel exports — and 61 percent want more weapons and supplies for Ukraine.

A WSJ poll shows 55 percent want more military aid to Ukraine, such as weapons and equipment, and 55 percent want more economic sanctions on Russia.

That means the president, right now, should put his stamp of approval on the Polish airplanes going to Ukraine. Mr. Putin says that would be an act of war, and there he goes again, cowering, looking for a desk under which to hide. Come out from under your desk, sir, and bark back at Mr. Putin.

Get the airplanes over there. It’s just a bunch of old soviet planes to begin with. First, you said yes, then Mr. Putin barked, and then you cowered. Why don’t you bark? We’re sending them all these other weapons, and Mr. Putin knows that. He’s just toying with you.

Stop letting Vladimir Putin control the play, as he has since last November. Your diplomacy failed, you still haven’t recovered, and the worst part is, the Ukrainian people are suffering badly. The great fact here is the bravery and courage of the Ukrainians and their president. They have stymied Russia.

The performance of the Red army has been a laughingstock. The so-called 40-mile convoy broke up because it was getting shelled heavily by the brave Ukrainians and the Russian soldiers were running away en masse.

The Russians were afraid of Reagan. The Russians were afraid of President Trump. As Machiavelli taught us 500 years ago, it is always better to be feared than loved. No one fears you, Mr. President.

If you stood up, Mr. President, if you barked back at Vladimir Putin, if you put him in his place, if you showed good, old-fashioned American backbone, you could drive him to the negotiating table for a peace deal. That is what a strong American president should and could do. Not if you wilt every time Mr. Putin does a bit of saber-rattling, though.

Act like a president, Mr. Biden, and this whole war against humanity in Ukraine will come to an end without spreading into World War III. Think about it.

From Mr. Kudlow’s broadcast on Fox Business News.