In a powerful speech Saturday in Poland, President Joe Biden framed the war in Ukraine as a once-in-a-generation battle for democracy, liberty and the fate of the free world.

That’s exactly why he mustn’t re-enter the Iran nuclear deal, which would be disastrous in every possible way for the cause of world peace and stability.

Biden said the fight against Russian President Vladimir Putin and “the darkness that drives autocracy” won’t be easy but must be waged “for the flame of liberty that lights the souls of free people everywhere.”

His tone was spot on. This conflict is much bigger than Russia versus Ukraine, which is one battle in the broader global war between democracy and autocracy.

Since the war began, the United States and Europe have imposed necessarily harsh sanctions on Russia and supplied Ukraine with billions of dollars in aid and advanced weapons. The time has come to tighten the noose on the Kremlin even further. A Russian win would set the West back in our mission to ensure the endurance of democracy globally.

But a renewed nuclear deal would sabotage Western interests, too, allowing two rogue powers to work together against America, with Russia leveraging Iran for relief from Western-imposed sanctions in exchange for Russia helping Iran do the same.

It simply strains credulity for the United States to impose debilitating sanctions against Putin vis-à-vis Ukraine while also entering a deal with Russia and another undemocratic state — Iran — that includes porous sanctions, provides these two countries with billions of dollars and creates a framework allowing Iran to become a nuclear power, thus further jeopardizing the free world.

The original 2015 deal — which gave Iran sanctions relief in exchange for restrictions on its nuclear program — was fatally flawed. It amounted to a win for Iran and its allies and a major setback for America and the West. And now, amid unprecedented levels of international instability, it’s clear that a 2022 deal would be even worse and have catastrophic consequences.

The original deal famously involved a large cash payment to Iran. Given the current closeness of Iran and Russia, the United States cannot in any shape, manner or form provide economic incentives to Iran when its principal partner is facing sanctions for a brutal invasion.

The 2015 agreement was filled with holes. It failed to address Iran’s ballistic missile program, which allowed Tehran to unrestrictedly build and test deadly weapons.

And it was next to impossible for the United States to know the full details of the Iranian nuclear program and whether Tehran was abiding by the accord’s guidelines. Instead of forcing Iran to stop developing nuclear weapons, the deal merely compelled Tehran to become more covert.

The deal’s sunset clauses were also problematic. Even if Iran were to again abide by the deal, the provisions have already started to expire and will end completely after 2030 — after which the Iranians are free to revitalize their nuclear program on a potentially even larger scale.

The problems don’t end there. The reinstated deal would fund terrorism in the Middle East and further destabilize the region. Its sanctions relief would provide the rogue state with tens of billions of dollars — some of which Tehran will funnel to Bashar al-Assad’s murderous Syrian regime and terrorist groups like Hezbollah and Hamas.

To that end, the deal also imperils Israel, America’s closest Middle Eastern ally, in a way that threatens the security of the Jewish state and of Jews worldwide.

Israel, the Middle East’s only democracy, remains in Iran’s nuclear crosshairs. A new deal would not only legitimize Iran’s nuclear ambitions — curtailing Israel’s ability to make important decisions with regard to its own national security — but would also give terrorist groups such as Hezbollah and Hamas a nuclear umbrella under which they would be free to wage war on Israel.

Ultimately, the Biden administration’s desperate and misguided effort to reinstate the deal hands Russia, Iran and other rogue states a win and directly endangers America and the West. It must change course.

If the United States stands for regime change in Russia — as Biden indicated in his speech on Saturday and a follow-up with reporters days later — we should certainly advocate a similar policy for Iran, where the mullahs lack popular support, the economy is in free fall and protests have been frequent over the past few years.

Take a page from your Poland speech, Mr. President. Call out, don’t aid, Russia and Iran if you want to promote the cause of freedom and enhance the chances of democracy’s emergence everywhere possible.

Douglas Schoen is founder and partner in Schoen Cooperman Research, a polling and consulting firm whose past clients include President Bill Clinton and Mayor Michael Bloomberg. Andrew Stein is a former New York City Council president.