Nippon Steel would move its U.S. headquarters to Pittsburgh where its acquisition target U.S. Steel is based if the deal goes through, an executive said, adding to the pledges from the Japanese steelmaker to secure the transaction.

Nippon Steel's proposed $15-billion takeover of U.S. Steel has drawn sharp criticism in the United States where President Joe Biden said last week the asset should remain domestically owned, while his opponent in the upcoming November election, Donald Trump, promised to block the deal if he is reelected.

The Japanese company, the world's fourth-biggest steelmaker, has been in talks with the United Steelworkers (USW), a labor union key for Biden and Trump in the upcoming November elections and which so far was opposing the deal.

"Not only are we keeping the Pittsburgh headquarters — which other bidders would not be able to do — but we are planning to move Nippon Steel's existing U.S. headquarters from Houston to Pittsburgh," Executive Vice President Takahiro Mori, Nippon Steel's key negotiator on the deal, was quoted as saying.

In comments released in a U.S. Steel document to the U.S. Securities and Exchange Commission overnight, Mori said his company remained engaged with the union and has offered a number of specific commitments on job security, investments, and other interests.

Nippon Steel would honor all agreements currently in place between U.S. Steel and the union, will not cut jobs, close facilities, or move production overseas, Mori reiterated.

The basic labor agreement between U.S. Steel and the union is expiring on Sept. 1, 2026, according to a proxy statement by U.S. Steel, and the company's shareholders are due to vote in the merger proposal April 12.

Nippon Steel plans to close the deal by the end of September, keeping the U.S. Steel brand name, and has secured a $16 billion financing commitment from Japanese banks.

The combined group should have 86 million tons of annual crude steel output capacity, narrowing the gap with the world's top steelmaker China Baowu Steel Group, and will advance the technological push toward carbon neutrality set for 2050.