Selling United States Steel to Nippon Steel would pose a risk to national security as well as to the entire American steel industry, the United Steelworkers (USW) said in a letter to Treasury Secretary Scott Bessent.

The influential union that runs most of the steelmaker¡¯s plants said the risks cannot be overcome in any scenario in which Nippon Steel exercises influence over U.S. Steel¡¯s decision-making. The union called the Japanese firm a ¡°serial unfair trader¡± and said it contributes to global overcapacity, echoing U.S. President Donald Trump¡¯s often-used tough-on-trade rhetoric.

The comments indicate the union that led the push to kill the deal during former U.S. President Joe Biden¡¯s term hasn¡¯t budged, even as Trump shifts between several positions and awaits a review of the deal. Trump¡¯s decision to take another look at the deal raised hopes among investors the sale might be revived, though Trump repeatedly has said he does not want Nippon Steel to hold a majority stake in U.S. Steel.

On April 7 Trump directed the Committee on Foreign Investment in the United States, on which Bessent sits as the panel¡¯s chair, to determine ¡°whether further action¡± is needed and ordered a report within 45 days.

¡°No mitigation measures will be sufficient to secure our domestic steelmaking capabilities and meet our national security needs,¡± USW President David McCall wrote in the letter.

At the time of Trump¡¯s order, Nippon Steel said it was pleased with the decision. U.S. Steel said the order validates its board of directors¡¯ decision to challenge Biden¡¯s ¡°unlawful¡± order to block the deal.

Shares of the steelmaker have been on a roller coaster since the beginning of the month. Optimism over Trump¡¯s review was offset by multiple subsequent comments reiterating the president¡¯s long-held position that he doesn¡¯t want to see U.S. Steel owned by a foreign entity.