TOKYO, Jan 12 (Reuters) - Nippon Steel said on Friday President Eiji Hashimoto will become CEO and chairman effective April 1, remaining at the helm as the top Japanese steelmaker aims to complete a deal to take over U.S. Steel .

Executive Vice President Tadashi Imai and head of Nippon Steel's initiative to decarbonise the steel-making process, will take the president and chief operating officer (COO) posts, the company said in a statement.

Hashimoto last month struck a $14.9 billion deal to acquire the iconic U.S. steelmaker but faces a tough road ahead as the United Steelworkers union and some lawmakers have criticized the acquisition. The White House has also pledged "serious scrutiny" of the deal.

In order for him to stay on top of the deal among other planned investments, Nippon Steel reinstated CEO and COO titles which do not exist under the current structure.

"To maintain management continuity, I will keep management responsibility as CEO for the time being," Hashimoto told a news conference.

Asked about the outlook for the U.S. Steel deal, Hashimoto reiterated that he believed the deal would go through as it provided benefits to the United States, such as a hefty investment and advanced technology that Nippon Steel has.

"We'll be able to complete the deal if we carefully deal with various issues, together with U.S. Steel," he said.

Since taking the current job in 2019, Hashimoto has undertaken drastic restructuring, including the closure of several domestic mills, while changing the negotiation formula with its key industry customers such as Toyota Motor so that it can swiftly pass on rising material costs to their product prices.

Overseas, Hashimoto made a flurry of major investments, buying two Thai steelmakers and taking a 20% stake in Canadian miner Teck Resources' coking coal unit.

(Reporting by Kantaro Komiya and Yuka Obayashi; Editing by Chang-Ran Kim and Emelia Sithole-Matarise)