Ukraine is running out of money for the war with Russia, and also out of allies that can stretch their budgets to help. So its remaining patrons in the European Union are reaching for creative, and risky, ways to solve the problem.

Essentially, some powerful European leaders want to use Russia’s own assets — currently frozen in place in Belgium — to engineer a loan for Kyiv that could support its war efforts for years to come.

The plans’ champions say they are worth the financial risk, because Europe must do whatever is necessary to show President Vladimir V. Putin of Russia that he should not expect Ukraine to crater anytime soon.

That view was distilled on Thursday by Friedrich Merz, the chancellor of Germany, in an opinion piece he wrote for The Financial Times.

“Moscow will only come to the table to discuss a cease-fire when it realizes that Ukraine has greater staying power,” Mr. Merz wrote.

“We need a new impetus to change Russia’s calculations,” he added. “Now is the moment to apply an effective lever that will disrupt the Russian president’s cynical game of buying time and bring him to the negotiating table.”

Here’s how that lever might work:

Europe would use Russia’s assets as collateral.

The plan Mr. Merz sketched out on Thursday features a novel use of hundreds of billions of dollars of Russian assets that were frozen in Europe after Russia invaded Ukraine in 2022. Mr. Merz would use those assets to underpin an interest-free loan to Ukraine of about $160 billion. Europe currently funnels the interest it earns on those assets to Ukraine, but it’s far less: about $8 billion last year.

Germany and Belgium have opposed past efforts to seize Russia’s assets in full and to give them to Ukraine, partly for fear of setting a dangerous legal precedent. Mr. Merz’s plan breaks from that position, but not entirely. He was careful to say the effort would not violate property rights, meaning the assets themselves would not be touched.

Instead, Europe would use Russia’s assets as a sort of loan collateral. Countries would, at least initially, sign up to backstop parts of the loan. If the assets were to somehow disappear — for example, if sanctions expired and Russia got its money back — and Ukraine could not repay creditors, European governments would be on the hook to do so.

The plan is similar to one outlined earlier this month by Ursula von der Leyen, the president of the European Commission, though not identical.

The German version would eventually shift the burden of guaranteeing the loan to the European Union, not member countries, as von der Leyen’s plan would do. It would also require Ukraine to use the money for defense and to buy weapons made in Europe — a tacit slap at the Trump administration, which has stopped sending weapons to Ukraine free of charge and insisted that European countries buy American arms to give to the Ukrainians.

European leaders appear to have few alternatives.

President Trump has made it clear that the United States will not provide additional financial support to Ukraine, even as he grows more frustrated with Mr. Putin for not following through on what Mr. Trump believed was a promise to swiftly negotiate an end to the war.

There are few other trees to shake. While Germany approved extensive borrowing for military spending in a deal Mr. Merz brokered shortly before he took office, Europe’s largest countries are struggling to bring their budgets more in balance. That includes France, another leader of the so-called Coalition of the Willing that backs Ukraine.

So Ms. von der Leyen and Mr. Merz turned elsewhere.

“We need to work urgently on a new solution to finance Ukraine’s war effort on the basis of the immobilized Russian assets,” Ms. von der Leyen said in her State of the Union address this month in Brussels.

There is no agreement yet, and much could go wrong.

In Mr. Merz’s opinion piece, he wrote that he would raise his proposal at a meeting with European leaders in Copenhagen next week in the hopes of reaching a deal by the end of next month. That would mean hammering out differences between his plan and Ms. von der Leyen’s and possibly overcoming objections from other countries.

Even if adopted soon, any plan would involve extensive financial engineering and most likely months of careful legal planning.

It would also punt difficult political and financial decisions years into the future, possibly until after the war ends. Most notably, both plans rest on the idea that somehow, someday, Russia will agree to pay for the reconstruction of Ukraine — even though Mr. Putin has thus far stuck to demands for ending the war on his terms.

“Ukraine will only pay back the loan once Russia pays for the reparations,” Ms. von der Leyen said.

If the war were to end with no reparation agreement, Europe would need to finally decide whether to confiscate the frozen Russian assets to pay off the loan. That is a step beyond what Mr. Merz appears ready to take, at least for now.