By Kevin Buckland and Kiyoshi Takenaka TOKYO (Reuters) -Japan Prime Minister Shigeru Ishiba asked U.S. President Joe Biden to allay concerns in the Japanese and U.S. business communities over the status of Nippon Steel's planned acquisition of U.

TOKYO -- Nippon Steel's plan to buy U.S. Steel has entered a new phase with the companies' declaration of a full-scale legal war against the U.S. government. They hope the lawsuits will overturn President Joe Biden's order to give up the acquisition.

The usually reticent ally is making it clear that it will not go quietly in its fight to overturn President Biden’s decision to block Nippon Steel’s $14.1 billion takeover bid of U.S. Steel, with Prime Minister Shigeru Ishiba warning this week that the rejection could have real consequences for the bilateral relationship,

The merger had become highly politicized ahead of the November U.S. presidential election, with Democrat Biden and Republican President-elect Donald Trump pledging to kill it as they wooed voters in the swing state of Pennsylvania where U.S. Steel is headquartered. United Steelworkers union President David McCall opposed the tie-up.

The bid by Japan’s Nippon Steel to buy U.S. Steel may have a new lease on life, now that the Biden Administration pushed back the deadline it imposed for the Japanese steelmaker to abandon its plan to acquire the storied Pittsburgh company.

President-elect Donald Trump has also expressed strong opposition to Japanese ownership of infrastructure giant.

Takahiro Mori said Nippon Steel's proposed acquisition of U.S. Steel does not bring any national security risks, despite Joe Biden's insistence otherwise.

The proposed deal kicked up an election year political maelstrom across America’s industrial heartland and quickly drew vows by Biden and Trump from the campaign trail in a critical battleground state to block the deal.