In a letter sent Sunday to Cleveland-Cliffs, the head of U.S. Steel said no board would review a proposal that put a price ahead of an “appropriate” discussion on the terms of a buyout.

“Pushing our Board to do so is in essence a demand that it breach its fiduciary duties,” said David Burritt, U.S. Steel’s president and CEO.

Burritt added that his company has “no choice” but to reject what he said was an “unreasonable proposal.”

Cleveland-Cliffs on Sunday made the terms of the July 28 offer public, saying it offered to buy out U.S. Steel for a 50% cash and 50% stock offer that put the value of the company at $35 per share.

“Although we are now public, I do look forward to continuing to engage with U.S. Steel on a potential transaction, as I am convinced that the value potential and competitiveness to come out of a combination of our two iconic American companies is exceptional,” Lourenco Goncalves, the chairman, president and CEO of Cleveland-Cliffs said.

Cleveland-Cliffs added that the United Steelworkers union said it would endorse the proposed transaction. If sanctioned, the acquisition would create the fourth-largest steel company in the world, outside of China.

Shares in Cleveland-Cliffs were up around 3% to trade at $15.16 per share.

U.S. Steel reported adjusted net earnings for the second quarter of $483 million, sharply lower than $1.1 billion during the same period in 2022. Like others in the commodities sector, earnings for U.S. Steel were hurt by lower prices.

The company sold its flat-rolled steel for an average $1,088 per ton during the second quarter, compared to $1,339 during the same period last year.

The situation was no different for Cleveland-Cliffs, though it realized a higher sale price for its products than U.S. Steel.