President Biden on Thursday is expected to express concerns over Nippon Steel's planned $14.9 billion acquisition of Pittsburgh's U.S. Steel, ahead of next month's White House visit by Japanese Prime Minister Fumio Kishida.

Why it matters: U.S. Steel picked Japan's Nippon over domestic rival Cleveland-Cliffs, because it preferred a national security review by CFIUS to an antitrust review by the Justice Department.

• Were CFIUS to oppose the acquisition, its recommendation would go directly to Biden.

What he'll say: "U.S. Steel has been an iconic American steel company for more than a century, and it is vital for it to remain an American steel company that is domestically owned and operated."

The bottom line: Biden is playing to his labor union base, as the USW had preferred Cleveland-Cliffs. But it remains unlikely that CFIUS will recommend Biden block the deal, given that Japan is a strategic U.S. ally.

Go deeper: United Steelworkers union blasts $15B U.S. Steel-Nippon deal