TOKYO (Reuters) -The U.S. administration's policy shift to introduce high tariffs will increase the strategic importance of Nippon Steel's ( NISTF ) business development in the U.S. market, the top Japanese steelmaker's CEO, Eiji Hashimoto, said on Thursday.

Hashimoto was speaking at a press conference in Tokyo a day after Nippon Steel ( NISTF ) closed its $14.9 billion acquisition of U.S. Steel, confirming an unusual degree of power for President Donald Trump after the Japanese company's 18-month struggle to close the purchase.

The companies also disclosed details of a national security agreement inked with the Trump administration, which gives the president the authority to name a board member as well as a non-economic golden share.

The measures represent an unusual level of control conceded by the companies to the government to save the deal, after a rocky path to approval spurred by high-level political opposition.