Updated 11:50am: Adds United Steelworkers union response.

US Steel (NYSE:X) David Burritt said Wednesday the company would close steel mills and likely move its headquarters out of Pittsburgh if its planned sale to Nippon Steel (OTCPK:NPSCY) (OTCPK:NISTF) collapses. US Steel shares rose 2.6%.

In an interview with The Wall Street JournalBurritt said the nearly $3B Nippon Steel (OTCPK:NPSCY) (OTCPK:NISTF) has pledged to invest in US Steel’s (X) older mills is critical to keeping them competitive and maintaining workers’ jobs.

“We wouldn’t do that if the deal falls through,” Burritt told WSJ. “I don’t have the money.”

The CEO also said in the interview that Nippon Steel (OTCPK:NPSCY) (OTCPK:NISTF) would bring investment and the latest steelmaking technology to US Steel’s (X) older mills in Gary, Indiana, and its Mon Valley Works near Pittsburgh, and described the opposition to the proposed acquisition by the Japan-based company as “puzzling and confusing.”

“Up until now, Burritt has described USS as a world class steel company, but now he is making baseless and illegal threats, saying if the transaction with Nippon is rejected, the future of US Steel as a viable steel company is at risk,” United Steelworkers President Dave McCall said in a statement on Wednesday. “His reckless statements and mismanagement are the only true obstacles to US Steel remaining a sustainable steel company.”

Democratic presidential nominee Kamala Harris said earlier this week that US Steel (X) should remain domestically owned and operated; President Biden, Republican presidential nominee Donald Trump, several members of Congress, and the United Steelworkers union also have lined up against the deal.

For its part, Nippon Steel (OTCPK:NPSCY) (OTCPK:NISTF) said Wednesday that US Steel (X) would remain a US company headquartered in Pittsburgh with a board comprised mostly of Americans if the deal is concluded.