(Adds dropped word in headline)

(Reuters) - U.S President Donald Trump formally approved Nippon Steel's ( NISTF ) fraught $14.9 billion bid for U.S. Steel on Friday, capping a tumultuous 18-month effort by the companies, beset by union opposition and two national security reviews. 

Trump signed an executive order saying the tie-up could move forward if the companies signed an agreement with the Treasury Department resolving national security concerns posed by the deal. The companies then announced they had signed the agreement, fulfilling the conditions of Trump's directive and effectively garnering approval for the merger.

"We look forward to putting our commitments into action to make American steelmaking and manufacturing great again," the companies said in the statement, thanking Trump.

They added the agreement includes $11 billion in new investments to be made by 2028 as well as governance, production and trade commitments. A golden share would be issued to the U.S. government, the companies added without providing further detail.

Reuters previously reported that Nippon would invest an additional $3 billion for a new mill after 2028.

The takeover will set up the ailing American steel icon to receive the critical investment, and allow Nippon Steel ( NISTF ) to capitalize on a host of American infrastructure projects, as its foreign competitors face steel tariffs of 50%. It also absolves the Japanese firm of paying $565 million in breakup fees if the companies failed to secure approvals.

A GREAT PARTNER

While many investors saw approval as likely after Trump headlined a rally on May 30 giving his vague blessing to an "investment" by Nippon Steel ( NISTF ), which he described as a "great partner", Friday's announcement was hardly guaranteed.

Shares of U.S. Steel had dipped earlier on Friday after a Nippon Steel ( NISTF ) executive told the Japanese Nikkei newspaper that its planned takeover of U.S. Steel required "a degree of management freedom" to go ahead after Trump earlier had said the U.S. would be in control with a golden share.

The bid, first announced by Nippon Steel ( NISTF ) in December 2023, has faced opposition from the start. Both Democratic former President Joe Biden and Trump, a Republican, asserted last year that U.S. Steel should remain U.S.-owned, as they sought to woo voters ahead of the presidential election in Pennsylvania, where the company is headquartered.

Biden in January, shortly before leaving office, blocked the deal on national security grounds, prompting lawsuits by the companies, which argued the national security review they received was biased. The Biden White House disputed the charge.

The steel companies saw a new opportunity in the Trump administration, which began on January 20 and opened a fresh 45-day national security review into the proposed merger in April.

But Trump's public comments, ranging from welcoming a simple "investment" in U.S. Steel by the Japanese firm to floating a minority stake for Nippon Steel ( NISTF ), spurred confusion.