(Bloomberg) -- JPMorgan Chase & Co. bought Argentine pesos last month on behalf of the US Treasury as Secretary Scott Bessent tried to shore up the country’s libertarian leader before a pivotal election, according to two letters sent Thursday by Senator Elizabeth Warren.

It’s the first public confirmation of JPMorgan’s exact role in the sweeping rescue effort the US mounted as President Javier Milei’s government reeled from weeks of market volatility heading into the October midterm race. While the bank’s participation in Argentina’s currency market was known, Warren’s letter clarifies that the Wall Street giant bought for the Treasury.

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One letter addressed to Bessent, who has heavily criticized Warren’s stand on Argentina, asked Treasury to provide more details on its financial lifeline for Milei. The other letter, addressed to New York Federal Reserve President John Williams, called for transparency.

In that one, Warren quoted a response from JPMorgan to her original inquiry on Oct. 24. “JPMorgan does transact open market operations for the US government (Treasury Department) via its fiscal agent the Federal Reserve,” the bank said. “As part of this business, we have executed purchases of Argentine pesos.”

Given “the public significance of the US government’s bailout of Argentina’s financial markets” and its implications for both foreign and domestic policy, Warren told Williams “the NY Fed owes the American public a clear accounting of its role.”

To her point, neither government has detailed how much the Treasury bought in pesos, nor the terms of a $20 billion swap line they signed. Besides Bessent’s social media posts, Treasury hasn’t released a single statement about the currency exchange.

A spokesperson confirmed that the New York Federal Reserve received Warren’s letter and will respond. Neither the US Treasury nor JPMorgan immediately replied to requests for comment.

Other banks, such as Goldman Sachs Group Inc., Bank of America Corp. and Citigroup Inc., declined to provide details to Warren, according to responses sent by her office. Wells Fargo & Co. confirmed it didn’t participate in any Argentine financial transactions that Warren inquired about. Bloomberg reported last month that Citi had sold pesos to the Treasury via the Fed.

Since Milei’s party convincingly won the Oct. 26 midterms, the US rescue package moved to the back burner while Argentine assets rallied. Bessent said afterward that markets should cover Argentina’s financing needs, a shift from his whatever-it-takes rhetoric in October.

JPMorgan Chief Executive Officer Jamie Dimon, who visited Buenos Aires and met with Milei before the vote, told Reuters on Wednesday that $20 billion in private financing from Wall Street banks for Argentina’s government “may not be necessary” anymore.

Milei may soon find out if Bessent is right about markets. He’ll meet with bankers Friday in New York to discuss investment opportunities in Argentina.

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