US President Joe Biden has issued an order to block Nippon Steel's planned buyout of US Steel.

In a statement released on Friday, Biden said there is credible evidence the Japanese firm "might take action that threatens to impair the national security of the United States."

Biden also said Nippon Steel and US Steel should "take all steps necessary to fully and permanently abandon the Proposed Transaction no later than 30 days after the date of this order."

The deal was first announced in December 2023.

The US Committee on Foreign Investment failed to reach a consensus on possible security threats in the deal by the December 23 deadline. It then referred the case to Biden.

White House National Security spokesperson John Kirby told reporters Friday that President Biden's order to block Nippon Steel's acquisition of US Steel will not affect the US-Japan alliance.

He was asked whether Biden's decision to deny a close ally would cast doubt on the reliability of the US as a partner.

Kirby responded that the decision is not about Japan, but about the US keeping one of the country's largest steel producers as an American-owned company.

He added the decision is not about the "extraordinary, close relationship and alliance" the US has with Japan.

Meanwhile, the leader of the United Steelworkers union, or USW, has welcomed President Biden's order. But the company's CEO strongly condemned the decision.

USW International President David McCall said in a statement the union has "no doubt" the decision is the "right move" for its members and US national security.

He expressed USW's confidence that "with responsible management, U.S. Steel will continue to support good jobs, healthy communities and robust national and economic security well into the future."

Union members have consistently opposed the Japanese firm's proposed acquisition and criticized its responses.

US Steel President and CEO David Burritt called Biden's action "shameful and corrupt" in a statement on X.

Burritt said Biden "insulted Japan, a vital economic and national security ally, and put American competitiveness at risk."

He accused Biden of making the decision while refusing to even meet with management to learn the facts.

Burritt stressed that Nippon Steel's investment guarantees a great future for US Steel, its employees, communities and the United States.

He added his company intends to fight Biden's "political corruption."