Senior U.S. officials have stepped up their efforts to lead Western governments to use hundreds of billions of dollars of frozen Russian central bank reserves to help Ukraine, according to three people who spoke on the condition of anonymity to describe internal conversations.

The intensifying push to use the assets for Ukraine comes as U.S. and European governments that support Kyiv encounter new domestic political roadblocks for their plans to send taxpayer money to the war effort, although officials insist the matters are unrelated. The Kremlin has an estimated $300 billion frozen in various bank accounts throughout Western countries, but experts have warned that simply taking that money would face legal challenges and pose major financial risks.

Congress dropped U.S. aid to Ukraine last month from a measure to extend government operations into November at the urging of House Republicans, a growing number of whom strongly oppose assistance for Ukraine’s war effort resisting Russia’s aggression. The White House had sought $20.6 billion for Ukraine over the summer, but the Senate pared that back to $6 billion, and then the House forced all of it out of the short-term spending law.

U.S. officials are adamant that Russian bank reserves are not a substitute for new emergency military and economic aid from Washington, which Ukraine needs to survive the next several months of the war. Even the most aggressive and optimistic advocates for redirecting the bank holdings believe it would take months — if not more than a year — for the money to reach Kyiv. And most of Russia’s reserves by far are held in Europe, where central bankers have expressed strong reservations about the impact of a seizure on their economies. If Washington acted alone, it could only make use of the estimated $5 billion held in the United States — a tiny share of the $300 billion of Russian money held around the world.

But within the Biden administration, the case for encouraging the West to redirect the assets is growing, even as some U.S. officials worry that the money might not be able to be used to pay to fight the war, but only for reconstruction.

On Wednesday, meeting with leading Western financial officials in Morocco, Treasury Secretary Janet L. Yellen endorsed a European proposal to tax the wartime earnings of the Russian bank assets and transfer the proceeds to Ukraine — an intermediate step that could take effect quickly. Ukrainian officials have discussed using the tax proceeds along with some of the seized Russian assets as collateral to raise far greater sums from private investors, according to two other people with knowledge of the matter, who also spoke on the condition of anonymity to discuss private conversations. That would free Ukraine to borrow money on capital markets without having to risk as much of its own scarce reserves.

On Wednesday, the Belgian government announced the creation of a $1.8 billion fund for Ukraine paid for by tax revenue from profits generated on seized Russian central bank assets. Most of the Russian money held in Europe is at the Belgian-based clearinghouse Euroclear. (The money will be used to help Ukraine with military support, civilian aid and refugee assistance, a government spokesman said.)

Besides the GOP divisions over Ukraine, NATO member Slovakia recently elected a pro-Russian leader opposed to additional aid for Kyiv. Using Russian reserves would have the obvious political upside of not imposing greater costs on Western taxpayers.

“It is certainly back now as part of the discussion,” said one person briefed on internal talks by senior U.S. and European financial officials. “The U.S. has become much more open to not just seizing, but also using the Russian reserves.”

In the years before launching its full-scale invasion of Ukraine, Russia amassed $600 billion in foreign currencies from selling oil and gas to the West. This “war chest” was intended to give the Kremlin a financial backstop against the West if it ever were hit with broad economic sanctions.

To safeguard the money, Russian President Vladimir Putin put more than half of the funds in Western accounts, with roughly $200 billion kept in Europe alone. Then Russia sent troops on a failed mission to decapitate the government in Kyiv in February 2022. Within days, the U.S. and European governments froze the assets, cutting Putin off from the reserves and eliciting a sharp rebuke from Moscow.

Since then, the funds have sat untouched in bank accounts in countries such as France, Germany and Austria, with smaller amounts sequestered in Japan, Australia, the United States and Canada. In May, the Group of Seven Western industrialized nations announced in a joint statement that the assets “will remain immobilized until Russia pays for the damage it has caused to Ukraine.”

But as the war has turned into a protracted stalemate, a growing chorus of experts has pushed for more immediate action.

In September, Harvard law professor Laurence Tribe, who has been influential with Biden for decades, published a 124-page report articulating the legality of seizing the funds. Tribe’s position echoed the calls of Larry Summers, another Harvard professor who also has informally advised Biden for decades. Summers has joined former World Bank president Robert B. Zoellick and former U.S. State Department counselor Philip D. Zelikow in backing the economic case for redirecting the assets.

In Congress, meanwhile, Sens. James E. Risch (R-Idaho) and Sheldon Whitehouse (D-R.I.) also have released a bipartisan bill to authorize the administration to act.

“It would be insane — literally insane — to say that we can’t do this until post-armistice, until hostilities have already ended,” Tribe said in an interview. “I’ve done my best to persuade them, because there’s no good argument against doing this, and the need now is greater than ever.”

Summers has discussed the matter with senior Ukrainian officials, including the country’s prime minister and finance minister, according to one person familiar with the matter, who spoke on the condition of anonymity to describe the private exchange.

“This is the rare case where the politically expedient thing is also the right thing to do,” Summers said. “Using Russian reserves rather than American taxpayer money is the right thing on economic grounds and moral grounds. It is surely better politics, and without accessing Russian resources, it’s inevitable that support for Ukraine will cannibalize support for other priorities like climate change, pandemic prevention and Africa.”

Some Western nations have moved to facilitate such a strategy. Canada last year passed a budget implementation bill that gave its government new powers to seize the assets of individuals or entities on its sanctions list and to put the proceeds toward compensating victims and reconstructing foreign states “adversely affected by a grave breach of international peace and security.”

Chrystia Freeland, Canada’s deputy prime minister and finance minister, has said she can “think of no more appropriate source of that funding than confiscated Russian assets.”

“For sure, this is kind of pushing the boundary of sanctions, seizure, forfeiture,” said a Western government official with knowledge of discussions about the matter, who spoke on the condition of anonymity because of not being authorized to speak publicly on the subject. “But there seems to kind of an internationally growing consensus of . . . who is going to pay for this? Is this a Western responsibility, or does the Kremlin have a role to play as well?”

And, yet, enormous legal and financial hurdles remain.

If the Europeans confiscated the funds, some financial experts fear other governments would decide to take their money out of the euro zone more broadly.

Lee C. Buchheit, a professor at the University of Edinburgh Law School, and Paul Stephan, a professor at the University of Virginia School of Law, also have written that “outright expropriation” would trigger constitutional safeguards unless the country involved is at war with the United States, which is not the case with Russia.

“The constraint has not been a lack of policy imagination or political will; it has been a lack of an available legal pathway,” said Daleep Singh, who served as deputy director at the White House National Economic Council for Biden and now is at PGIM Fixed Income.

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