Nippon Steel has hired former U.S. Secretary of State Mike Pompeo to help complete a proposed purchase of United States Steel, a deal facing bipartisan opposition from Donald Trump and U.S. President Joe Biden.

Pompeo, who served as the U.S.¡¯ top diplomat under Trump, will be an adviser to the Japanese company for its $14.1 billion purchase, according to people familiar with the matter, speaking on condition of anonymity to discuss the move. The deal¡¯s fate is unclear as it undergoes a national security review and faces opposition by the United Steelworkers union.

Nippon Steel confirmed the move in a written statement, praising Pompeo¡¯s record. Pompeo said the U.S. should expand its manufacturing base by partnering with allies in a statement also provided by the company.