As Russian warplanes pound Ukrainian cities with cluster bombs, President Volodymyr Zelensky has been begging the United States and its allies to make a decision: Either stop the carnage by establishing a no-fly zone over Ukraine or give Ukrainians the fighter jets to do it themselves. “If you cannot shut the sky now . . . then give me the planes,” Zelensky said.

On Tuesday, Warsaw answered Zelensky’s call. The Polish foreign minister announced that Poland was ready to give its entire fleet of Soviet-era MiG-29 fighters to Ukraine “immediately and free of charge” — offering to send them to a U.S. air base in Germany and asking the United States “to provide us with used aircraft with corresponding operational capabilities” in exchange. The United States would then transfer the MiGs to the Ukrainian Air Force.

Incredibly, the Biden administration scoffed at Poland’s offer. “We do not believe Poland’s proposal is a tenable one,” said Pentagon spokesman John Kirby. “The prospect of fighter jets . . . departing from a U.S./NATO base in Germany to fly into airspace that is contested with Russia over Ukraine raises serious concerns for the entire NATO alliance.”

So let’s get this straight: On Sunday, Secretary of State Antony Blinken gave Poland a “green light” to send aircraft to Ukraine from Polish NATO bases, but sending them to Ukraine from a U.S. NATO base in Germany is not “tenable”? What is the difference exactly? The Biden administration is worried that sending fighter jets from NATO territory into Ukraine could provoke Russia to declare us co-belligerents in Ukraine. But Poland is as much NATO territory as Germany.

Moreover, the United States and its allies have already acknowledged that we are providing Ukraine with Stinger antiaircraft missiles. Those missiles have the exact same role and purpose as the MiG fighter jets: to shoot down and kill Russian aircraft. Those Stinger missiles are not magically appearing in Ukraine. They are not being teleported to Ukrainian forces. They are being sent to Ukraine by the United States from NATO bases in Europe. How is sending fighter jets to carry out the same mission any different?

And with all respect, the airspace over Ukraine is not “contested” in any legal sense. It is the sovereign airspace of a sovereign nation that has been unlawfully invaded by an unjust aggressor. That unjust aggression does not give Putin veto power. The only permission we need to send those planes is from Zelensky.

The Biden administration’s obsession with not giving Russia a pretext to declare us co-belligerents is not only weak; it is strategically pointless. As Latvian Defense Minister Artis Pabriks points out, “If . . . the Kremlin would like to fight a war against NATO or Europe, they could always find a reason.”

The fact is, after a week of shameful inaction, Poland has come to Ukraine’s aid — and exposed the Biden administration as the real obstacle to answering Zelensky’s impassioned pleas for help. NATO has plenty of planes it could provide. Poland, Romania, Slovakia and Bulgaria have dozens of Soviet-designed MiG-29 and Su-27 fighters, which Ukrainian pilots know how to fly.

But instead of leading and finding a way to get those jets to Ukraine as quickly as possible, the Biden administration has spent the past week making excuses for inaction. When Poland — understandably concerned about giving up MiGs just as the Russian threat to their territory has grown dramatically — asked for F-16 fighter jets to replace the lost capacity, the administration claimed it did not have sufficient inventory. If we didn’t have enough F-16s to give the Poles immediately, though, Biden could have offered to deploy more U.S. fighter squadrons to guard their airspace until we do. Or the Defense Department could have asked Lockheed Martin to divert some F-16s headed for other U.S. allies to Poland. If there was a will, there was a way.

But the problem, it turns out, is a lack of will. Instead of finding a solution, the White House tried to blame Warsaw for the delays and told reporters it was a “sovereign decision” for Polish leaders to make.

Well, now Poland has made that sovereign decision — and put the ball entirely in Biden’s court. If those planes are not flying over Kyiv as soon as possible, Biden will be to blame. He alone will be responsible for denying Zelensky the vital military capability he has said he needs to save innocent Ukrainian lives. Every day that he dithers, innocent Ukrainians are being slaughtered. As Zelensky told NATO’s leaders last week, “All the people who will die from this day will die because of you . . . because of your weakness.”

Those words should now be ringing in Biden’s ears. Sending American pilots to enforce a no-fly zone over Ukraine risks putting us in direct combat with Russia. But there is absolutely no excuse for denying Ukraine the aircraft it needs to patrol its own skies.

Poland’s MiGs can be flying in Ukraine tonight. If they are not, blame lies with one man: Joe Biden.

Marc A. Thiessen is on Twitter, @marcthiessen.