KYIV, Ukraine — As Ukrainian officials considered how to sway a skeptical President Donald Trump to continue supporting their country, one strategy was to appeal to Trump’s so-called businesslike approach and offer him a trade — say, rare earth minerals — to get something in return.

Now Trump says he’s interested.

Speaking to reporters in the Oval Office on Monday, Trump said the United States wants Ukrainian rare earth minerals — such as lithium, uranium and titanium — in exchange for the security assistance that Ukraine depends on for its defense against Russia’s invasion.

“We’re looking to do a deal with Ukraine, where they’re going to secure what we’re giving them with their rare earth and other things,” Trump said.

With continued U.S. support for Ukraine in doubt since Trump’s election, officials in Kyiv regarded Trump’s interest in Ukraine’s rare earth commodities as a positive development that could get him invested in the country’s future. Ukrainian President Volodymyr Zelensky first suggested providing the United States with the materials during his meeting with Trump ahead of the November election.

A senior Ukrainian official, speaking on the condition of anonymity to discuss a sensitive matter, said Tuesday that Zelensky’s administration is “ready to sign documents about joint agreements” and that “having a strategic U.S. interest in Ukraine is a key component to our security in the future.”

Trump’s interest in Ukraine’s offer of a barter for military aid could serve as a road map for how countries negotiate with his administration going forward. While repeatedly criticizing past U.S. spending on support for Ukraine, Trump has promised to soon broker a deal to end the three-year war with Russia. But that left some Ukrainian officials uneasy over whether the United States — by far the biggest supplier of weapons to Ukraine — would continue sending critical aid in the event a ceasefire isn’t reached this year.

Trump’s comments Monday offered an indication that he is willing to continue arming Kyiv — as long as there is something in it for Washington. And with many of Ukraine’s rare earth minerals concentrated in the country’s east, where Russia has occupied the most land and continues gaining ground, Trump might be more incentivized to help Ukraine push back the invading forces, the senior Ukrainian official said.

Probably of particular interest to Trump are Ukraine’s prospective deposits of lithium — used for high-tech components, such as those used in microchips and electric cars. Russia is also interested in Ukraine’s natural resources, and one major lithium reserve is within 10 miles of the front line in the Donetsk region. Analysts have estimated that Moscow has already managed to seize control of more than $12 trillion-worth of Ukrainian energy assets, metals and minerals.

Exactly how many mineral resources Ukraine has is something of a mystery, though they are believed to be worth trillions. The Ukrainian official acknowledged that estimates are outdated and that new surveys would need to be done according to international standards.

During a forum hosted by the Kyiv-based We Build Ukraine think tank last month, Denys Aloshin, the director of strategic development at UkrLithiumMining, said lithium resources in one central Ukrainian deposit are estimated at 42 million tons, according to their study.

Part of the Ukrainian pitch to Trump was that China has already invested in receiving rare earth minerals from Africa and Latin America, so this marks an opportunity for the United States to compete with its adversary.

Kremlin spokesman Dmitry Peskov said Trump wants Kyiv “to buy aid” in a sign that Washington is no longer willing to provide weapons to Ukraine free anymore.

German Chancellor Olaf Scholz had perhaps the harshest criticism of Trump’s bid to tie future assistance to Ukraine’s rare earth resources, saying such a move “would be very selfish, very self-centered.” He added that Ukraine would need those minerals to rebuild its struggling economy after the war.

“It’s about Ukraine being able to finance its reconstruction,” he told reporters in Brussels late Monday.

A European diplomat said Ukraine has discussed with its allies using earnings from those resources for reconstruction — “not so much just giving them to another state or exchanging them for weapons.”

The viability of Trump’s proposal could depend “on how exactly it’s meant by Trump,” the diplomat said, speaking on the condition of anonymity to share internal deliberations.

He noted it would be somewhat different if the plan was to reach agreements on trade conditions or exclusive licensing access.

“For now, we are in the process of figuring out what is a negotiating technique and what is meant literally,” the official said. In his comments on Monday, Trump suggested the minerals would be “a guarantee” for funneling money and equipment to Ukraine, and repeated his long-held insistence that Europe should be carrying more weight. “Look, we have an ocean in between. They don’t,” he said. “It’s more important for them than it is for us.”

In preparation for Trump’s return to the White House and what they expect will be a more quid pro quo approach from the new administration, European leaders have made overtures, including suggestions they could buy more weapons from U.S. companies.

A second European diplomat said countries are “open to looking at things in a more transactional way,” though “not at all costs, and not on all issues.”

European countries have already been increasing their military spending to the highest levels since the Cold War — partly after Trump’s past harping that NATO allies should spend more on defense. But this has also been driven by Russian threats and growing recognition that European security should be less dependent on the whims of Washington. NATO Secretary General Mark Rutte has in recent months warned that European countries will have to spend even more.

European countries have also moved to boost their share of funding for Kyiv to hedge against possible changes in U.S. policy. But as major European allies face economic woes, maintaining the flow of funds and weapons in the long run will be a struggle, especially if the United States scales back its sizable chunk of military aid. Many acknowledge that losing American political support on Ukraine could also shift the tide of the war in Russia’s favor.

Ukraine has struggled on the battlefield as nearly three years of fighting has worn down weapons stocks and depleted its ranks. Russia has also has also hammered cities with nightly bombardments targeting the country’s critical infrastructure.

On Tuesday, a Russian missile strike on the northeastern city of Izyum destroyed part of the city council building, killing at least five people and injuring 50 others.

Francis reported from Brussels. David L. Stern and Kostiantyn Khudov in Kyiv and Natalia Abbakumova in Riga, Latvia, contributed to this report.

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